Ligands for imaging cardiac innervation

ABSTRACT

Novel compounds that find use as imaging agents within nuclear medicine applications (PET imaging) for imaging of cardiac innervation are disclosed. These PET based radiotracers may exhibit increased stability, decreased NE release (thereby reducing side effects), improved quantitative data, and/or high affinity for VMAT over prior radiotracers. Methods of using the compounds to image cardiac innervation are also provided. In some instances the compounds are developed by derivatizing certain compounds with 18F in a variety of positions: aryl, alkyl, a keto, benzylic, beta-alkylethers, gamma-propylalkylethers and beta-proplylalkylethers. Alternatively or additionally, a methyl group a is added to the amine, and/or the catechol functionality is either eliminated or masked as a way of making these compounds more stable.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/448,575, filed May 14, 2010, which is a national stage filing under35 U.S.C. § 371 of international application PCT/US2007/088500, filedDec. 21, 2007, which was published under PCT Article 21(2) in English,and claims benefit under 35 U.S.C. § 119(e) of U.S. provisionalapplication 60/877,211 filed Dec. 26, 2006, the disclosures of each ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

Novel compounds that find use as imaging agents within nuclear medicineapplications (e.g., PET imaging and SPECT imaging) are disclosed.Methods of using the compounds to image cardiac innervation are alsoprovided.

BACKGROUND OF THE INVENTION

Heart failure (HF) is a condition that afflicts increasingly more peopleeach year. This condition is defined as the common end-stage of manyfrequent cardiac diseases (e.g. myocardial infarction, pressureoverload, volume overload, viral myocarditis, toxic cardiomyopathy), andis characterized by relentless progression. The resultant myocardialdamage from such events in conjunction with neurohormonal and cytokineactivation, is suspect for the causes of chamber remodeling of theheart, an initial phase of HF. Early diagnosis of HF is difficultbecause the remodeling process precedes the development of symptoms bymonths or even years. The current diagnostic tests (e.g. two dimensionalechocardiogram coupled with Doppler flow studies) only reveal changes inthe heart in the late stages of the disease. To date, no cure for HFexists. Early diagnosis is a key factor in achieving a good prognosisand management of this disease.

An imaging agent that identifies patients in early HF would enableimmediate treatment and life-style improvements for those living withthis disease. In the past, researchers have investigated a variety ofbiological markers found in HF to develop methods for detection of earlystages of HF. The cardiac sympathetic nervous system (CSNS), which ispart of the autonomic nervous system, was found to be one of thebiological markers of interest.

The autonomic nerve system, which plays a crucial role in regulatingcardiac function, consists of the CSNS and the cardiac parasympatheticnervous system (CPNS). In the two branches of the cardiac autonomicinnervations, the CSNS and CPNS, postganglionic sympathetic neuronscommunicate with each other via the neurotransmitter norepinephrine(NE). These branches work in finely tuned opposition to each other inthe heart. Thus stimulus to the sympathetic nerve system causesincreased contractility, acceleration of heart rate and conduction,which is mediated by the action of NE on post synaptic β₁ adrenoceptors.Stimulation of the parasympathetic nerves on the other hand, leads to adecrease in heart rate and conduction. This is mediated by action ofacetylcholine on postsynaptic M₂ muscarinic acetylcholine receptors.

NE is the neurotransmitter of postganglionic sympathetic neurons. NE isstored in vesicles within the neurons and is released by Ca⁺² mediatedexocytosis into the synaptic cleft upon nerve depolarization. Most ofthe norepinephrine released is returned to the neuron by thenorepinephrine transporter (NET; also known as “Uptake-1” mechanism) andrepackaged into storage vesicles by the vesicular monoamine transporter(VMAT). The remaining amount of NE in the synaptic cleft binds topostsynaptic β1 adrenoceptors controlling heart contractility,acceleration of heart rate and heart conduction. Tissue concentrationsof NE in the normal heart are generally considered to be reliablemarkers of regional sympathetic nerve density, which are uniformlydistributed throughout the heart.

Abnormalities in cardiac innervation have been implicated in thepathophysiology of many heart diseases, including sudden cardiac death,congestive heart failure, diabetic autonomic neuropathy, myocardialischemia and cardiac arrhythmias Heart failure is characterized by ahyperadrenergic state whereby increased systemic levels of NE andincreased local spillover of catecholamines occurs. It has beendocumented that there is a reduction in cardiac uptake-1 density orfunction in tissue samples of both human patients and animal models,which may be the reason for the increased amount of systemic NE observedin myocardium tissue. Development of methods to assess physiologicalchanges of NE uptake-1 in the myocardium are therefore highly desirable.

As disclosed in United States Patent Application Publication No.20060127309 (herein incorporated by reference in its entirety), medicalradionuclide imaging (e.g., Nuclear Medicine) is a key component ofmodern medical practice. This methodology involves the administration,typically by injection, of tracer amounts of a radioactive substance(e.g., radiotracer agents, radiotherapeutic agents, andradiopharmaceutical agents), which subsequently localize in the body ina manner dependent on the physiologic function of the organ or tissuesystem being studied. The radiotracer emissions, most commonly gammaphotons, are imaged with a detector outside the body, creating a map ofthe radiotracer distribution within the body. When interpreted by anappropriately trained physician, these images provide information ofgreat value in the clinical diagnosis and treatment of disease. Typicalapplications of this technology include detection of coronary arterydisease (e.g., thallium scanning) and the detection of cancerousinvolvement of bones (e.g., bone scanning). The overwhelming bulk ofclinical radionuclide imaging is performed using gamma emittingradiotracers and detectors known as “gamma cameras.”

Recent advances in diagnostic imaging, such as magnetic resonanceimaging (MRI), computerized tomography (CT), single photon emissioncomputerized tomography (SPECT), and positron emission tomography (PET)have made a significant impact in cardiology, neurology, oncology, andradiology. Although these diagnostic methods employ different techniquesand yield different types of anatomic and functional information, thisinformation is often complementary in the diagnostic process. Generallyspeaking, PET uses imaging agents labeled with the positron emitterssuch as ¹⁸F, ¹¹C, ¹³N and ¹⁵O, ⁷⁵Br, ⁷⁶Br and ¹²⁴I. SPECT uses imagingagents labeled with the single-photon-emitters such as ²⁰¹Tl, ⁹⁹Tc,¹²³I, and ¹³¹I.

Glucose-based and amino acid-based compounds have also been used asimaging agents Amino acid-based compounds are more useful in analyzingtumor cells, due to their faster uptake and incorporation into proteinsynthesis. Of the amino acid-based compounds, ¹¹C- and ¹⁸F-containingcompounds have been used with success. ¹¹C-containing radiolabeled aminoacids suitable for imaging include, for example, L-[1-¹¹C]leucine,L-[1-¹¹C]tyrosine, L-[methyl-¹¹C]methionine and L-[1-¹¹C]methionine.

PET scans involve the detection of gamma rays in the form ofannihilation photons from short-lived positron emitting radioactiveisotopes including, but not limited to ¹⁸F with a half-life ofapproximately 110 minutes, ¹¹C with a half-life of approximately 20minutes, ¹³N with a half-life of approximately 10 minutes and ¹⁵O with ahalf-life of approximately 2 minutes, using the coincidence method. ForPET imaging studies of cardiac sympathetic innervation, carbon-11 (¹¹C)labeled compounds such as [¹¹C]meta-hydroxyephedrine (HED) arefrequently used at major PET centers that have in-house cyclotrons andradiochemistry facilities. Recently the nuclear medicine market has seena substantial increase in stand-alone PET imaging centers that do nothave cyclotrons. These satellite-type facilities typically use2-[¹⁸F]fluoro-2-deoxy-D-glucose (FDG) for PET imaging of canceroustumors.

SPECT, on the other hand, uses longer-lived isotopes including but notlimited to ^(99m)Tc with a half-life of approximately 6 hours and ²⁰¹Tlwith a half-life of approximately 74 hours. The resolution in presentSPECT systems, however, is lower than that presently available in PETsystems.

Radiotracers targeting each branch of cardiac autonomic innervation havebeen developed. The number of tracers developed for the sympatheticneurons however is far more than those developed for the parasympatheticneurons. There are two reasons for this. First, the NET is nonselectiveand will readily transport structural analogs of NE into the sympatheticvaricosity. The choline uptake carrier on the other hand is highlyselective. Second, there is a dense population of the sympathetic nervesin the left ventricular wall as compared to the parasympathetic neuronsfound in the thin walls of the atria and conduction nodes. This hastherefore, made imaging the sympathetic neurons easier. The structuresbelow are examples of radiolabel led catecholamines and catecholamineanalogues, and guanadines used for studying cardiac sympathetic neurons.

Radiolabelled Catecholamines and Catecholamine Analogues, and GuanidinesUsed for Studying Cardiac Sympathetic Neurons

[¹¹C]Dopamine ([¹¹C]DA) and 6-[¹⁸F]fluorodopamine (6-[¹⁸F]FDA) have beenused to image dogs and baboons respectively. 6-[¹⁸F]FDA showed rapiduptake and clearance, and good images of the heart. [¹¹C]Norepinephrine([¹¹C]NE) has been used to obtain planar images of canine heart andclearly visualized the left ventricular myocardium in a cynomologousmonkey. 6-[¹⁸F]Fluoronorepinephrine (6-[¹⁸F]FNE) has also been used toimage the baboon heart and showed high uptake and retention. Myocardialkinetics of [¹¹C]epinephrine ([¹¹C]EPI) has been extensively studied andis handled in a similar manner to NE and has been used to assessneuronal changes in cardiac transplant patients.

The catecholamine analogues like 1R,2S-6-[¹⁸F]-fluorometaraminol(6-[¹⁸F] FMR), [¹¹C]hydroxyephedrine ([¹¹C]HED) and [¹¹C]phenylephrine([¹¹C]PHEN) have also been used very effectively to study thesympathetic nerve system. [¹²³I]-meta-Iodobenzylguanidine (MIBG) isanother extensively studied catecholamine analog that shows neuronaluptake as well as uptake by the cardiac myocytes, when studyingsympathetic nerve fibers of the heart. Studies with MIBG allowclinicians to map the regional distribution of nerve fibers in the heartusing imaging devices found in all nuclear medicine clinics. MIBG isalso used for diagnostic imaging and radiotherapy of adrenergic tumors,such as neuroblastoma and pheochromocytoma. [¹²³I]MIBG has been used todelineate nerve damage while [¹¹C]HED has been used to demonstrateneuronal abnormalities in a number of heart conditions includingtransplanted hearts, cardiomyopathy, acute myocardial infarction andcardiac diabetic neuropathy. MIBG is a SPECT tracer, however, andtherefore does not provide quantitative information.

Lastly, [¹²⁵I]-CAAP was the first ¹²⁵I-radiolabeled1-carboxamidino-4-phenyl-piperazine. Comparison studies of [¹²⁵I]-CAAPwith [¹²⁵I]-MIBG in tissue distribution studies in rats demonstratedequivalent uptake of the radiotracer in heart tissue. The uptake andretention of the compounds in the myocardium tissue are speculated to bedue to the same mechanism of action, which recognizes the guanidinefunctionality in both substrates. NET uptake-1 is a possible mode ofaction. Several positron emitting radiotracers were therefore developedas shown below.

MIBG and Positron Emitting Analogues

Of the three benzylguanidine PET tracers developed only one,4-[¹⁸F]fluoro-3-iodobenzylguanidine ([¹⁸F]FIBG) demonstrated uptake andbehavior similar to MIBG in vivo.

All the tracers mentioned above give valuable information but have theirlimitations. These include metabolic instability (NE, FNE, DA, FDA,PHEN, EPI and CAAP) or pharmacologically active norepinephrine release(FMR). MIBG also has its drawbacks. It has considerable extraneuronaluptake mediated by passive diffusion and by the uptake-2 (membranetransport) mechanism. And, being a SPECT agent, like CAAP, MIBG does notgive quantitative information and has other associated limitations.There is therefore a need for tracers that will show the followingcharacteristics:

a) stability,

b) not cause NE release (thereby reducing side effects),

c) give quantitative information, and/or

d) high affinity for VMAT.

SUMMARY OF THE INVENTION

The present invention provides novel compounds that find use as imagingagents within nuclear medicine applications (e.g., PET imaging and SPECTimaging). Methods of using the compounds to image cardiac innervationare also provided. In some embodiments of the present invention, the PETbased radiotracers exhibit increased stability, decreased NE release(thereby reducing side effects), improved quantitative information,and/or high affinity for VMAT. In certain embodiments, these tracers arebased on compounds that are derivatized with ¹⁸F in a variety ofpositions: aryl, alkyl, a keto, benzylic, beta-alkylethers,gamma-propylalkylethers and beta-proplylalkylethers, as shown in theirstructures below. In alternative embodiments, a methyl group α is addedto the amine, and/or the catechol functionality is either eliminated ormasked as a way of making these molecules more stable.

One embodiment of the present invention provides PET based radiotracersas illustrated in the general structure I:

wherein m=0, 1, or 2; n=0, 1, 2, and A is O or absent. R, R₁, R₂, and R₃are independently selected from the group consisting of H, OR₄, F, Cl,CF₃, Br, I, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NH)NHR₅, C(═O)NHR₅, NHC(═O)NR₅, NHNR₅, SO₂OR₅, and imaging moiety Im.Q consists of bridging groups that can be present between Y and Z, andto R₂. The Q bridging groups can independently be selected from thegroup consisting of CH₂, CH, CR₅, N, NH, NR₅, O and S in such acombination as to create a chemically stable structure. The substituentsW, X, Y and Z may independently be selected from the group consisting ofH, OR₄, NR₄, F, Cl, Br, I, Im, aryl, and heteroaryl. R₄ and R₅ may be H,alkyl, aryl or heteroaryl substituents. In an alternative embodiment,the alkyl, aryl or heteroaryl substituents may be substituted withvarious functional groups as hereinafter described.

In certain embodiments, the present invention provides a PET basedradiotracer having structure II as follows:

wherein linking groups B, D, E, F, and G are independently selected fromthe group consisting of a bond, alkyl (C₁-C₅; preferably C₂), aryl,aralkyl, alkylaryl, heteroaryl, alkoxy, alkylamino, aminoalkyl, aryloxy,alkoxyalkyl, thioalkyl, and heterocyclyl. R₆ through R₁₂ areindependently selected from the group consisting of H, OR₄, F, Cl, CF₃,Br, I, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NH)NHR₅, C(═O)NHR₅, NHC(═O)NR₅, NHNR₅, SO₂OR₅, and imaging moiety Im.R₄ and R₅ may be H, alkyl, aryl or heteroaryl substituents. And, Im isselected from the group consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, ¹³¹I, ^(99m)Tc,¹⁵³Gd, ¹¹¹In, and ⁹⁰Y.

In certain embodiments, the present invention provides a PET basedradiotracer compound having the following Structure Alpha:

wherein n=0, 1, 2, 3 and A is O or absent. R, R₁, R₂ and R₃ areindependently selected from the group consisting of H, OR₄, F, Cl, Br,I, CF₃, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NR₄)OR₅, NR₄(C(═NR₅)NHR₆, C(═NR₄)NHR₅, C(═O)NHR₄, NR₄C(═O)NR₅,NR₄NR₅, SO₂OR₄, and Im. The substituents W, X, Y and Z can independentlybe selected from the group consisting of H, OR₄, N(R₄)₂, F, Cl, Br, I,CF₃, Im, aryl, and heteroaryl. R₄, R₅, and R₆ are H, alkyl, aryl orheteroaryl substituents. And, the imaging moiety, Im, can be selectedfrom the group consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, ¹³¹I, ^(99m)Tc, ¹⁵³Gd, or¹¹¹In.

In addition, in a further embodiment, the invention also provides a PETradiotracer compound having Structure Beta:

wherein n=0, 1, 2, 3 and A=0 or is absent. R, R₁, R₂ and R₃ areindependently selected from the group consisting of H, OR₄, F, Cl, Br,I, CF₃, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NR₄)OR₅, NR₄(C(═NR₅)NHR₆, C(═NR₄)NHR₅, C(═O)NHR₄, NR₄C(═O)NR₅,NR₄NR₅, SO₂OR₄, and Im. The substituents W and X can independently beselected from the group consisting of H, OR₄, N(R₄)₂, F, Cl, Br, I, CF₃,Im, aryl, and heteroaryl. Y and Z can be selected from the groupconsisting of CH, CH₂, O, N, NR₇, and CH═CH. Bridging group Q is absentor selected from the group consisting of CH, CR₄, CH₂, N, NR₄, NH, S,and O. R₄, R₅, and R₆ are H, alkyl, aryl or heteroaryl substituents.

In certain embodiments, the present invention provides a PET basedradiotracer having Structure Chi as follows:

wherein R through R₂ are independently selected from the groupconsisting of H, OR₃, F, Cl, Br, I, CH₂F, OCH₂CH₂F, alkyl (C₁-C₄), aryl,heteroaryl, C(═O)R₃, CO₂R₃, and Im. Im is a imaging moiety and isselected from the group consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, and ¹³¹I. R₃ canbe an H, alkyl, aryl or heteroaryl substituent.

In certain embodiments, the present invention provides a PET basedradiotracer having Structure Delta as follows:

wherein linking groups B, D, E, F and G are independently selected fromthe group consisting of a bond, alkyl (C₁-C₅; preferably C₂), aryl,aralkyl, alkylaryl, heteroaryl, alkoxy, alkylamino, aryloxy, andalkoxyalkyl. R₈ through R₁₄ are independently selected from the groupconsisting of H, OR₃, F, Cl, Br, I, CH₂F, OCH₂CH₂F, alkyl (C₁-C₄), aryl,heteroaryl, C(═O)R₃, CO₂R₃, and Im. R₃, R₄, R₅, and R₆ can independentlybe selected from the group consisting of H, alkyl, aryl, aralkyl,heteroaryl, alkylamino, alkyloxy, and aryloxy. The imaging moiety, Im,can be selected from the group consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, ¹³¹I,^(99m)Tc, ¹⁵³Gd, and ¹¹¹In.

A preferred embodiment describes the PET based radiotracer compoundN-[3-bromo-4-(3-[¹⁸F]fluoropropoxy)-benzyl]-guanidine hydrochloride, asillustrated in Structure Epsilon below:

A further embodiment describes a method of imaging cardiac innervationcomprising the steps of: administering an effective amount of one ormore of the compounds disclosed above, to a patient; detecting gammaradiation emitted by said compound; and forming an image therefrom.

The present invention is directed to these, as well as other importantends, hereinafter described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a first series of representative cardiac short- and long-axisimages with RP1190-18 in a non-human primate according to an embodimentof the invention. These images were acquired during 40-60 min afterinjection and were decay corrected. The myocardium was defined withrelatively high activity in the lung.

FIG. 2 is a second series of representative cardiac short- and long-axisimages with RP1195-18 in a non-human primate according to a furtherembodiment of the invention. These images were acquired during 40-60 minafter injection and were decay corrected. The myocardium was clearlydefined with minimal background lung and liver interference.

DETAILED DESCRIPTION OF THE EMBODIMENTS Definitions

Unless otherwise indicated, the term “lower alkyl” as may be employedherein alone or as part of another group includes both straight andbranched chain hydrocarbons containing 1 to 8 carbons, and the terms“alkyl” and “alk” as may be employed herein alone or as part of anothergroup includes both straight and branched chain hydrocarbons containing1 to 20 carbons, preferably 1 to 10 carbons, more preferably 1 to 8carbons, in the normal chain, such as methyl, ethyl, propyl, isopropyl,butyl, t-butyl, isobutyl, pentyl, hexyl, isohexyl, heptyl,4,4-dimethylpentyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, undecyl,dodecyl, the various branched chain isomers thereof, and the like aswell as such groups including 1 to 4 substituents such as halo, forexample F, Br, Cl or I or CF₃, alkyl, alkoxy, aryl, aryloxy, aryl(aryl)or diaryl, arylalkyl, arylalkyloxy, alkenyl, alkynyl, cycloalkyl,cycloalkenyl, cycloalkylalkyl, cycloalkylalkyloxy, hydroxy,hydroxyalkyl, acyl, alkanoyl, heteroaryl, heteroaryloxy,cycloheteroalkyl, arylheteroaryl, arylalkoxycarbonyl, heteroarylalkyl,heteroarylalkoxy, aryloxyalkyl, aryloxyaryl, alkylamido, alkylamino,alkanoylamino, arylcarbonylamino, nitro, cyano, thiol, haloalkyl,trihaloalkyl and/or alkylthio.

Unless otherwise indicated, the term “cycloalkyl” as may be employedherein alone or as part of another group includes saturated or partiallyunsaturated (containing 1 or 2 double bonds) cyclic hydrocarbon groupscontaining 1 to 3 rings, any one of which may optionally be a spirosubstituted cycloalkyl, including monocyclicalkyl, bicyclicalkyl andtricyclicalkyl, containing a total of 3 to 20 carbons forming the rings,preferably 3 to 10 carbons, forming the ring and which may be fused to 1or 2 aromatic rings as described for aryl, which include cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyland cyclododecyl, cyclohexenyl,

any of which groups may be optionally substituted with 1 to 4substituents such as halogen, alkyl, alkoxy, hydroxy, aryl, aryloxy,arylalkyl, cycloalkyl, alkylamido, alkanoylamino, oxo, acyl,arylcarbonylamino, nitro, cyano, thiol and/or alkylthio and/or any ofthe alkyl substituents.

The term “heterocyclo”, “heterocycle”, “heterocyclyl” or “heterocyclicring”, as may be used herein, represents an unsubstituted or substitutedstable 4 to 7-membered monocyclic ring system which may be saturated orunsaturated, and which consists of carbon atoms, with one to fourheteroatoms selected from nitrogen, oxygen or sulfur, and wherein thenitrogen and sulfur heteroatoms may optionally be oxidized, and thenitrogen heteroatom may optionally be quaternized. The heterocyclic ringmay be attached at any heteroatom or carbon atom which results in thecreation of a stable structure. Examples of such heterocyclic groupsinclude, but is not limited to, piperidinyl, piperazinyl,oxopiperazinyl, oxopiperidinyl, oxopyrrolidinyl, oxoazepinyl, azepinyl,pyrrolyl, pyrrolidinyl, furanyl, thienyl, pyrazolyl, pyrazolidinyl,imidazolyl, imidazolinyl, imidazolidinyl, pyridyl, pyrazinyl,pyrimidinyl, pyridazinyl, oxazolyl, oxazolidinyl, isooxazolyl,isoxazolidinyl, morpholinyl, thiazolyl, thiazolidinyl, isothiazolyl,thiadiazolyl, tetrahydropyranyl, thiamorpholinyl, thiamorpholinylsulfoxide, thiamorpholinyl sulfone, oxadiazolyl and other heterocyclesdescribed in Katritzky, A. R. and Rees, C. W., eds. ComprehensiveHeterocyclic Chemistry The Structure, Reactions, Synthesis and Uses ofHeterocyclic Compounds 1984, Pergamon Press, New York, N.Y.; andKatritzky, A. R., Rees, C. W., Scriven, E. F., eds. ComprehensiveHeterocyclic Chemistry II: A Review of the Literature 1982-1995 1996,Elsevier Science, Inc., Tarrytown, N.Y.; and references therein.

The term “alkanoyl” as may be used herein alone or as part of anothergroup refers to alkyl linked to a carbonyl group.

The term “halogen” or “halo” as may be used herein alone or as part ofanother group refers to chlorine, bromine, fluorine, and iodine, withchlorine or fluorine or bromine sometimes being preferred.

Unless otherwise indicated, the term “aryl” or “Aryl” as may be employedherein alone or as part of another group refers to monocyclic andbicyclic aromatic groups containing 6 to 10 carbons in the ring portion(such as phenyl or naphthyl including 1-naphthyl and 2-naphthyl) and mayoptionally include one to three additional rings fused to a carbocyclicring or a heterocyclic ring (such as aryl, cycloalkyl, heteroaryl orcycloheteroalkyl rings). For example

and may be optionally substituted through available carbon atoms with 1,2, or 3 groups selected from hydrogen, halo, haloalkyl, alkyl,haloalkyl, alkoxy, haloalkoxy, alkenyl, tfifluoromethyl,trifluoromethoxy, alkynyl, cycloalkyl-alkyl, cycloheteroalkyl,cycloheteroalkylalkyl, aryl, heteroaryl, arylalkyl, aryloxy,aryloxyalkyl, arylalkoxy, alkoxycarbonyl, arylcarbonyl, arylalkenyl,aminocarbonylaryl, arylthio, arylsulfinyl, arylazo, heteroarylalkyl,heteroarylalkenyl, heteroarylheteroaryl, heteroaryloxy, hydroxy, nitro,cyano, thiol, alkylthio, arylthio, heteroarylthio, arylthioalkyl,alkoxyaiylthio, alkylcarbonyl, arylcarbonyl, alkylaminocarbonyl,arylaminocarbonyl, alkoxycarbonyl, aminocarbonyl, alkylcarbonyloxy,arylcarbonyloxy, alkylcarbonylamino, arylcarbonylamino, arylsulfinyl,arylsulfinylalkyl, arylsulfonylamino and arylsulfonaminocarbonyl and/orany of the alkyl substituents set out herein.

Unless otherwise indicated, the term “heteroaryl” as may be used hereinalone or as part of another group refers to a 5- or 6-membered aromaticring which includes 1, 2, 3 or 4 hetero atoms such as nitrogen, oxygenor sulfur. Such rings may be fused to an aryl, cycloalkyl, heteroaryl orheterocyclyl and include possible N-oxides as described in Katritzky, A.R. and Rees, C. W., eds. Comprehensive Heterocyclic Chemistry: TheStructure, Reactions, Synthesis and Uses of Heterocyclic Compounds 1984,Pergamon Press, New York, N.Y.; and Katritzky, A. R., Rees, C. W.,Scriven, E. F., eds. Comprehensive Heterocyclic Chemistry II: A Reviewof the Literature 1982-1995 1996, Elsevier Science, Inc., Tarrytown,N.Y.; and references therein. Further, “heteroaryl”, as defined herein,may optionally be substituted with one or more substituents such as thesubstituents included above in the definition of “substituted alkyl” and“substituted aryl”. Examples of heteroaryl groups include the following:

and the like.

Unless otherwise indicated, the term “lower alkoxy”, “alkoxy”, “aryloxy”or “aralkoxy” as may be employed herein alone or as part of anothergroup includes any of the above alkyl, aralkyl or aryl groups linked toan oxygen atom.

Unless otherwise indicated, the term “lower alkylthio”, alkylthio”,“arylthio” or “aralkylthio” as may be employed herein alone or as partof another group includes any of the above alkyl, aralkyl or aryl groupslinked to a sulfur atom.

The term “polyhaloalkyl” as may be used herein refers to an “alkyl”group as defined above which includes from 2 to 9, preferably from 2 to5, halo substituents, such as F or Cl, preferably F, such as CF₃CH₂, CF₃or CF₃CF₂CH₂.

The term “polyhaloalkyloxy” as may be used herein refers to an “alkoxy”or “alkyloxy” group as defined above which includes from 2 to 9,preferably from 2 to 5, halo substituents, such as F or Cl, preferablyF, such as CF₃CH₂O, CF₃O or CF₃CF₂CH₂O.

The terms “R_(n)” as used herein are to be construed with reference tothe specific structure in which are utilized and described, and may beused more than once.

PET based radiotracers for mapping the nervous system have beendeveloped in an attempt to address the limitations of priorradiotracers. In some embodiments of the present invention, the PETbased radiotracers are developed to exhibit increased stability,decreased NE release (thereby reducing side effects), improvedquantitative information, and/or high affinity for VMAT. In certainembodiments, these tracers are based on compounds that are derivatizedwith ¹⁸F in a variety of positions: aryl, alkyl, α keto, benzylic,beta-alkylethers, gamma-propylalkylethers and beta-proplylalkylethers,as shown in their structures below. In alternative embodiments, a methylgroup α is added to the amine, and/or the catechol functionality iseither eliminated or masked as a way of making these molecules morestable.

PET based radiotracers for mapping the cardiac sympathetic nerve systeminclude General Structures I and II:

Examples of compounds represented by General Structures I & II includethe following:

One embodiment of the present invention provides PET based radiotracersas illustrated in the General Structure I above, wherein m=0, 1, or 2;n=0, 1, 2, and A is O or absent. R, R₁, R₂, and R₃ are independentlyselected from the group consisting of H, OR₄, F, Cl, CF₃, Br, I, alkyl(C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN, C(═NH)NHR₅,C(═O)NHR₅, NHC(═O)NR₅, NHNR₅, SO₂OR₅, and imaging moiety Im. Q comprisesbridging groups that can be present between Y and Z, and to R₂. The Qbridging groups can independently be selected from the group consistingof CH₂, CH, CR₅, N, NH, NR₅, O and S in such a combination as to createa chemically stable structure. The substituents W, X, Y and Z mayindependently be selected from the group consisting of H, OR₄, NR₄, F,Cl, Br, I, Im, aryl, and heteroaryl. R₄ and R₅ may be H, alkyl, aryl orheteroaryl substituents. In an alternative embodiment, the alkyl, arylor heteroaryl substituents may be substituted with various functionalgroups selected from the group consisting of, but not limited to,halogen (F, Cl, Br, I), OH, NH₂, COOH, Im, COOR₁₃, CON(R₁₃)₂, SR₁₃,OR₁₃, NHC(═NH)NH₂, NHC(═O)NH₂, NHC(═O)N(R₁₃)₂, C(═NH)NH₂,C(═NR₁₃)N(R₁₃)₂ and N(R₁₃)₂, in which R₁₃ may be hydrogen, alkyl, arylor alkylaryl.

Another embodiment provides PET based radiotracers as illustrated in theGeneral Structure II above, wherein linking groups B, D, E, F and G areindependently selected from the group consisting of a bond, alkyl(C₁-C₅; preferably C₂), aryl, aralkyl, alkylaryl, heteroaryl, alkoxy,alkylamino, aryloxy, alkoxyalkyl, and heterocyclic. R₆ through R₁₂ maybe independently selected from the group consisting of H, OR₄, F, Cl,CF₃, Br, I, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NH)NHR₅, C(═O)NHR₅.NHC(═O)NR₅, NHNR₅, SO₂OR₅, and Im. R₄ and R₅ maybe H, alkyl, aryl or heteroaryl substituents, and Im is an imagingmoiety that may be selected from the group consisting of ¹⁸F, ⁷⁶Br,¹²⁴I, ¹³¹I, ^(99m)Tc, ¹⁵³Gd, ¹¹¹In, and ⁹⁰Y. And, provided that in thecase where any one of R₆-R₁₀ equals Im, the linking group B, D, E, F orG, which attaches the imaging moiety to the phenyl ring, contains atleast one atom.

Structure Alpha and Examples

A further embodiment provides PET based radiotracers as illustrated inStructure Alpha and non-limiting Examples above, which in its simplestform may be considered a hybrid of structures I and II. In StructureAlpha n=0, 1, 2, 3 and A is O or absent. R, R₁, R₂ and R₃ areindependently selected from the group consisting of H, OR₄, F, Cl, Br,I, CF₃, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NR₄)OR₅, NR₄(C(═NR₅)NHR₆, C(═NR₄)NHR₅, C(═O)NHR₄, NR₄C(═O)NR₅,NR₄NR₅, SO₂OR₄, and Im. The substituents W, X, Y and Z can independentlybe selected from the group consisting of H, OR₄, N(R₄)₂, F, Cl, Br, I,CF₃, Im, aryl, and heteroaryl. R₄, R₅, and R₆ are H, alkyl, aryl orheteroaryl substituents. In an alternative embodiment, any two of R₄,R₅, or R₆ may form a cyclic structure selected from the group consistingof —CH₂—CH₂—, —CH₂—CH₂—CH₂, —CH═CH—, —X═CH—, and —X—CH═CH—, wherein X isO, NH, N═, or NR₇, and wherein R₇ is an alkyl, aryl or heteroarylsubstituent. In a further alternative embodiment, the alkyl, aryl orheteroaryl substituents of R₄-R₇ may be substituted with variousfunctional groups selected from the group consisting of but not limitedto halogen (F, Cl, Br, I), OH, NH₂, COOH, Im, COOR₈, CON(R₈)₂, SR₈, OR₈,NHC(═NH)NH₂, NHC(═O)NH₂, NHC(═O)N(R₈)₂, C(═NH)NH₂, C(═NR₈)N(R₈)₂ andN(R₈)₂, in which R₈ may be hydrogen, alkyl, aryl or alkylaryl. Theimaging moiety, Im, is selected from the group consisting of ¹⁸F, ⁷⁶Br,¹²⁴I, ¹³¹I, ^(99m)Tc, ¹⁵³Gd, or ¹¹¹In, and can be present in either W—Zor R—R₇.

Structure Beta and Examples

In yet a further embodiment, PET based radiotracers are described asillustrated in Structure Beta and non-limiting Examples above. InStructure Beta n=0, 1, 2, 3 and A=O or is absent. R, R₁, R₂ and R₃ areindependently selected from the group consisting of H, OR₄, F, Cl, Br,I, CF₃, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₄, CO₂R₄, N(R₄)₂, CN,C(═NR₄)OR₅, NR₄(C(═NR₅)NHR₆, C(═NR₄)NHR₅, C(═O)NHR₄, NR₄C(═O)NR₅,NR₄NR₅, SO₂OR₄, and Im. The substituents W and X can independently beselected from the group consisting of H, OR₄, N(R₄)₂, F, Cl, Br, I, CF₃,Im, aryl, and heteroaryl. Y and Z can be selected from the groupconsisting of CH, CH₂, O, N, NR₇, and CH═CH. Bridging group Q is absentor selected from the group consisting of CH, CR₄, CH₂, N, NR₄, NH, S,and O. R₄, R₅, and R₆ are H, alkyl, aryl or heteroaryl substituents. Inan alternative embodiment, any two of R₄, R₅, or R₆ may form a cyclicstructure selected from the group consisting of —CH₂—CH₂—,—CH₂—CH₂—CH₂—, —CH═CH—, —X═CH—, and —X—CH═CH—, wherein X is O, NH, N═,or NR₇, and wherein R₇ is an alkyl, aryl or heteroaryl substituents. Ina further alternative embodiment, the alkyl, aryl or heteroarylsubstituents of R₄-R₇ may substituted with various functional groupsselected from the group consisting of but not limited to halogen (F, Cl,Br, I), OH, NH₂, COOH, Im, COOR₈, CON(R₈)₂, SR₈, OR₈, NHC(═NH)NH₂,NHC(═O)NH₂, NHC(═O)N(R₈)₂, C(═NH)NH₂, C(═NR₈)N(R₈)₂ and N(R₈)₂, in whichR₈ may be hydrogen, alkyl, aryl or alkylaryl. The imaging moiety, Im, isselected from the group consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, ¹³¹I, ^(99m)Tc,¹⁵³Gd, or ¹¹¹In, and can be present in either W—Z or R—R₇.

Structure Chi:

In an even further preferred embodiment, PET based radiotracers aredescribed as illustrated in Structure Chi above. R through R₂ ofStructure Chi are independently selected from the group consisting of H,OR₃, F, Cl, Br, I, CH₂F, OCH₂CH₂F, alkyl (C₁-C₄), aryl, heteroaryl,C(═O)R₃, CO₂R₃, and Im. Im is a imaging moiety and is selected from thegroup consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, and ¹³¹I. R₃ can be an H, alkyl,aryl or heteroaryl substituent. In an alternative embodiment the alkyl,aryl, aralkyl, alkylaryl or heteroaryl substituents of R-R₃ may besubstituted with functional groups selected from the group consisting ofbut not limited to halogen (F, Cl, Br, I), OH, NH₂, COOH, Im, COOR₄,CON(R₄)₂, SR₄, OR₄, NHC(═NH)NH₂, NHC(═O)NH₂, NHC(═O)N(R₄)₂, C(═NH)NH₂,C(═NR₄)N(R₄)₂ and N(R₄)₂, in which R₄ may be hydrogen, alkyl, aryl oralkylaryl.

Structure Delta:

A further embodiment describes PET based radiotracers as illustrated inStructure Delta above, wherein linking groups B, D, E, F and G areindependently selected from the group consisting of a bond, alkyl(C₁-C₅; preferably C₂), aryl, aralkyl, alkylaryl, heteroaryl, alkoxy,alkylamino, aryloxy, and alkoxyalkyl. R₈ through R₁₄ are independentlyselected from the group consisting of H, OR₃, F, Cl, Br, I, CH₂F,OCH₂CH₂F, alkyl (C₁-C₄), aryl, heteroaryl, C(═O)R₃, CO₂R₃, and Im. R₃,R₄, R₅, and R₆ can independently be selected from the group consistingof H, alkyl, aryl, aralkyl, heteroaryl, alkylamino, alkyloxy, andaryloxy. In an alternative embodiment any two of R₄, R₅, R₆, R₁₃, or R₁₄may form a cyclic structure selected from the group consisting of abond, —CH₂—, —CH₂—CH₂—, —CH₂—CH₂—CH₂—, —CH═CH—, —X═CH—, and —X—CH═CH—,wherein X is O, NH, N═, or NR₇, and wherein R₇ is an alkyl, aryl orheteroaryl substituent. In a further alternative embodiment, the alkyl,aryl or heteroaryl substituents of R₃-R₇ may be substituted with variousfunctional groups selected from the group consisting of but not limitedto halogen (F, Cl, Br, I), OH, NH₂, COOH, Im, COOR₄₅, CON(R₁₅)₂, SR₁₅,OR₁₅, NHC(═NH)NH₂, NHC(═O)NH₂, NHC(═O)N(R₁₅)₂, C(═NH)NH₂,C(═NR₁₅)N(R₁₅)₂ and N(R₁₅)₂, wherein R₁₅ may be hydrogen, alkyl, aryl oralkylaryl. The imaging moiety, Im, can be selected from the groupconsisting of ¹⁸F, ⁷⁶Br, ¹²⁴I, ¹³¹I, ^(99m)Tc, ¹⁵³Gd, and ¹¹¹In, and maybe present in either W—Z or R₄-R₇. And, provided that in the case whereany one of R₈-R₁₂ equals Im, the linking group B, D, E, F or G, whichattaches the imaging moiety to the phenyl ring, contains at least oneatom.

Structure Epsilon:

A preferred embodiment describes the PET based radiotracerN-[3-bromo-4-(3-[¹⁸F]-fluoropropoxy)-benzyl]-guanidine hydrochloride, asillustrated in Structure Epsilon above. Structure Epsilon may be derivedfrom Structure Alpha, wherein R₁, R₃, X and W are hydrogen, n is zero, Ris guanidine (NHC(═NH)NH₂), Y is bromine and Z is OCH₂CH₂CH₂ ¹⁸F.

Additional preferred compounds as part of the invention include thefollowing:

A further embodiment includes a method of imaging cardiac innervationcomprising the steps of: administering an effective amount of one ormore of the novel compounds herein set forth above, to a patient;detecting gamma radiation emitted by said compound; and forming an imagetherefrom. The method utilizes PET perfusion scanning or SPECT imagingtechniques available to the skilled artisan, or other methods which maybe employed.

There is also provided a composition useful in medical imaging whichcomprises one or more of the compounds hereinabove set forth, togetherwith one or more excipients.

The compounds hereinabove described may be synthesized by methodsavailable to the skilled artisan, which are in part further exemplifiedby the non-limiting Examples below.

EXAMPLES

The following examples are provided to demonstrate and furtherillustrate certain preferred embodiments of the present invention andare not to be construed as limiting the scope thereof.

General Experimental.

¹H NMR spectra were recorded on a Bruker Avance DRX 600 MHz spectrometeror on a Bruker Avance 300 MHz spectrometer. Chemical shifts are reportedin ppm from tetramethylsilane with the residual solvent resonanceresulting from incomplete deuteration as the internal standard (CDCl₃: δ7.25 ppm, CD₃CN: δ 1.94 ppm, DMSO-d₆: δ 2.50 ppm). Data are reported asfollows: chemical shift, multiplicity (s=singlet, d=doublet, t=triplet,q=quartet, quin=quintet, b or br=broad, m=multiplet), couplingconstants, and integration. ¹³C NMR spectra were recorded on a BrukerAvance DRX 150 MHz or on a Bruker Avance 75 MHz spectrometer withcomplete proton decoupling. Chemical shifts are reported in ppm fromtetramethylsilane with the solvent as the internal reference (CDCl₃: δ77.0 ppm, CD₃CN: δ 118.1 ppm, DMSO-d₆: δ 39.5 ppm). ¹⁹F NMR spectra wererecorded on a Bruker Avance DRX 565 MHz spectrometer. Chemical shiftsare reported in ppm relative to an external standard (CCl₃F; δ=0.00ppm). Low-resolution mass spectrometry was performed on an AgilentTechnologies 1100 Series LC/MS EST-MS (positive mode). High-resolutionmass spectrometry was performed on an Ionspec Ultima FTMS; ESI-MS(positive mode), or on an Agilent MSD-TOF; ESI-MS (positive mode).Melting points were determined using a Thomas-Hoover melting pointapparatus and are uncorrected.

Unless otherwise stated, all reactions were conducted under an inertatmosphere of dry nitrogen. Indicated temperatures refer to those of thereaction bath, while ambient laboratory temperature is noted as 22° C.Anhydrous dimethylformamide (DMF), dimethylsulfoxidc (DMSO),acetonitrile (McCN), pyridine, triethylamine (TEA), anddiisopropylethylamine (DIEA) were obtained from Aldrich in SureSearbottles. Absolute ethanol was obtained from Quantum Chemical Corp. Mercksilica gel, grade 9385, 230-400 mesh, 60 Å was used for flashchromatography. Ethyl acetate (EtOAc), chloroform (CHCl₃), methanol(MeOH), HPLC grade acetonitrile (MeCN), dichloromethane (DCM), ethylether, acetone, sodium hydroxide (NaOH), and hydrochloric acid (HCl)were obtained from Baker. 1-Trityl-1H-imidazole-2-amine was preparedaccording to a published procedure (U.S. Pat. No. 6,130,231,incorporated by reference in its entirety). 1-Bromo-2-fluoroethane waspurchased from Alfa Aesar. 3-Methoxy-4-fluorobenzonitrile was purchasedfrom TCI. MDCK cell membranes expressing human norepinephrinetransporter, and [³H]desipramine were purchased from Perkin-Elmer.[¹⁸F]NaF was obtained from PETNET Pharmaceutical Services (CummingsPark, Woburn, Mass.) on a MP1 anion exchange resin (BioRad) cartridge.Other reagents were obtained from Lancaster Synthesis, Inc.,Sigma-Aldrich Chemical Co, or Fluka Chemical Corp.

Example 1 Synthesis ofN-(4-Fluoro-3-(trifluoromethyl)benzyl)-1H-imidazol-2-amine

Part A—Preparation ofN-(4-Fluoro-3-(trifluoromethyl)benzyl)-1-trityl-1H-imidazol-2-amine

A solution of 4-fluoro-3-(trifluoromethyl)benzaldehyde (227 mg, 1.18mmol) and 1-trityl-1H-imidazole-2-amine (462.3 mg, 1.42 mmol) in toluene(40 mL) was heated at reflux for 6 h while using a Dean-Stark apparatusto remove water. The mixture was cooled to room temperature, treatedwith sodium triacetoxyborohydride (1.00 g, 4.70 mmol), and stirredovernight. The reaction was quenched by the addition of water (150 mL),and the layers were separated. The aqueous layer was extracted withethyl acetate (2×50 mL). The combined organic layers were dried (MgSO₄)and concentrated, and the resulting residue was purified by flashchromatography (40:60 EtOAc/hexanes) to yield the title compound as apale yellow solid (266 mg, 45%). ¹H NMR (CDCl₃, 300 MHz): δ 7.38-7.30(m, 9H), 7.24-7.14 (m, 6H), 7.14-6.93 (m, 3H), 6.71 (d, J=3.0 Hz, 1H),6.45 (d, J=3.0 Hz, 1H), 4.28 (d, J=6.0 Hz, 2H), 3.26 (t, J=6.0 Hz, 1H);¹³C NMR (CDCl₃, 75 MHz): δ 158.69 (d, J=253.5), 149.54, 141.52, 135.56,132.82 (d, J=8.2 Hz), 129.93, 128.16, 128.07, 125.86, 122.44,118.19-117.60 (m), 117.30, 116.48 (d, J=20.25 Hz), 73.91, 46.54. MS(ESI): 243.2 (Trt carbocation, 100).

Part B—Preparation ofN-(4-Fluoro-3-(trifluoromethyl)benzyl)-1H-imidazol-2-amine

A solution of the product of Part A (150 mg, 0.30 mmol) in 5:95triisopropylsilane/TFA (2.0 mL) was heated at 60° C. for 2 h, andconcentrated. The residue was dissolved in DCM (20 mL) and washed with5% Na₂CO₃ (10 mL). The organic layer was dried (Na₂SO₄) andconcentrated. The resulting crude product was purified by flashchromatography (MeOH/DCM, 10/90→15/85) to yield the title compound as alight gray oil (49.7 mg, 64%). ¹H NMR (CDCl₃, 600 MHz): δ 7.51 (d, J=6.0Hz, 1H), 7.50-7.46 (m, 1H), 7.10 (t, J=9.6 Hz, 1H), 6.57 (s, 2H), 5.31(bs, 3H), 4.41 (s, 2H); ¹³C NMR (CDCl₃, 150 MHz): δ 159.21 (d, J=254.4),149.86, 135.27, 132.82 (d, J=8.2 Hz), 126.04 (d, J=3.9 Hz), 122.69 (q,J=270.8 Hz), 119.02-118.36 (m), 117.55, 117.35 (d, J=20.7 Hz), 46.99;¹⁹F NMR (CDCl₃, 565 MHz): δ −61.39 (d, J=12.4 Hz), −116.39 (t, J=6.2Hz). MS (ESI): 260.2 (M+H, 100); HRMS calc'd for C₁₁H₁₀F₄N₃ (M+H):260.0805. Found: 260.0807.

Example 2 Synthesis of1-(2-(4-(2-fluoroethoxy)phenyl)-2-hydroxyethyl)guanidinium Chloride

Part A—Preparation of1-(2-Hydroxy-2-(4-hydroxyphenyl)ethyl)-2,3-bis(tert-butoxycarbonyl)guanidine

A solution of (+/−)-octopamine hydrochloride (500 mg, 2.89 mmol) andN,N′-bis(Boc)-1H-pyrazole-1-carboxamidine (1.13 g, 3.60 mmol) in DMF (10mL) was stirred for 1 h at ambient temperatures. The reaction mixturewas concentrated, and the residue was dissolved in EtOAc (60 mL). Thesolution was washed with 1 N KHSO₄ (2×30 mL) and 5% Na₂CO₃ (30 mL). Theorganic layer was dried (Na₂SO₄), concentrated, and purified by flashchromatography (EtOAc/hexane 30/70→50/50) to yield the title compound asa colorless solid (836 mg, 73%). ¹H NMR (CDCl₃, 600 MHz): δ 11.45 (bs,1H), 8.76 (s, 1H), 7.15 (d, J=8.4 Hz, 2H), 6.77 (d, J=8.4 Hz, 2H), 6.52(bs, 1H), 4.81-4.78 (m, 1H), 3.66-3.50 (m, 2H), 1.51 (s, 9H), 1.49 (s,9H); ¹³C NMR (CDCl₃, 150 MHz): δ 162.86, 157.52, 156.04, 153.19, 133.52,127.34, 115.65, 83.83, 80.07, 73.95, 49.49, 28.41, 28.26. MS (ESI):396.4 (M+H, 100), 340.3 (M+H−tBu, 15).

Part B—Preparation1-(2-(4-(2-Fluoroethoxy)phenyl)-2-hydroxyethyl)-2,3-bis(tert-butoxycarbonyl)guanidine

A mixture of the product of Part A (311 mg, 0.79 mmol), K₂CO₃ (163 mg,1.18 mmol), KI (1.2 mg, 0.0070 mmol), and 2-bromofluoroethane (59 μL,0.79 mmol) in DMSO (2.0 mL) was stirred at 50° C. for 3 h, followed byroom temperature overnight. Water (15 mL) was added and the mixture wasextracted with EtOAc (2×15 mL). The combined organic layers were washedwith saturated NaCl (10 mL), dried (Na₂SO₄) and concentrated. The cruderesidue was purified with flash chromatography (EtOAc/hexane) to yieldthe title compound as a colorless solid (177 mg, 51%). ¹H NMR (DMSO-d₆,300 MHz): δ 11.47 (s, 1H), 8.70 (s, 1H), 7.35-7.31 (m, 2H), 6.95-6.89(m, 2H), 4.85-4.82 (m, 2H), 4.69-4.66 (m, 1H), 4.28-4.25 (m, 1H),4.19-4.16 (m, 1H), 3.68-3.61 (m, 2H), 1.51 (s, 18H); ¹³C NMR (DMSO-d₆,75 MHz): δ 162.91, 158.21, 157.73, 153.21, 135.18, 127.42, 114.85,83.81, 82.13 (d, J=169.5 Hz), 79.96, 74.26, 67.42 (d, J=20.2 Hz), 49.82,28.44, 28.25. MS (ESI): 464.1 (M+Na, 6), 442.1 (M+H, 100), 386.1(M+H−tBu, 8).

Part C—Preparation of 1-(2-(4-(2-Fluoroethoxy)phenyl)-2-hydroxyethyl)guanidinium Chloride

The product of Part B (15.0 mg, 0.034 mmol) was dissolved in a solutionof dioxane (1.0 mL) and 37% aqueous HCl (4.0 mL), and allowed to standat ambient temperature for 40 min. The mixture was concentrated and theresulting residue was purified by HPLC using a Phenomenex Luna C18(2)column (250×21.2 mm, 10μ, 100 Å) using a 0.72%/min gradient of 0-18% ACNcontaining 0.1% formic acid at a flow rate of 20 mL/min. Pure fractionswere lyophilized to give a hygroscopic formate salt. This material wasre-lyophilized from 0.5 N HCl to give the title compound as a drycolorless solid (4.5 mg, 48%). ¹H NMR (1:1 CD₃CN/D₂O, 600 MHz): δ7.31-7.27 (m, 2H), 6.95-6.92 (m, 2H), 4.74-4.73 (m, 2H), 4.69-4.66 (m,1H), 4.25-4.17 (m, 2H), 3.34-3.28 (m, 2H); ¹³C NMR (1:1 CD₃CN/D₂O, 150MHz): δ 159.01, 158.42, 134.89, 128.56, 115.70, 83.62 (d, J=164.4 Hz),72.24, 68.44 (d, J=18.9 Hz), 49.31. MS (ESI): 224.3 (M+H−H₂O, 100); HRMScalc'd for C₁₁H₇FN₃O₂ (M+H): 242.1299. Found: 242.1297.

Example 3 Synthesis of 1-(4-(2-Fluoroethoxy)phenethyl)guanidiniumChloride

The product of Example 2, Part B (88.4 mg, 0.20 mmol) was dissolved in asolution of TFA (1.9 mL), triisopropylsilane (0.05 mL), and water (0.05mL). The reaction solution was heated at 55° C. for 10 min andconcentrated. The crude mixture was purified by HPLC using the procedureof Example 2, Part B. The product fraction was lyophilized yielding ahygroscopic solid.

Relyophilization from 0.5 N HCl gave the title compound as a drycolorless solid (12.4 mg, 24%). ¹H NMR (1:1 CD₃CN/D₂O, 600 MHz): δ7.18-7.14 (m, 2H), 6.90-6.87 (m, 2H), 4.75-4.65 (m, 2H), 4.22-4.15 (m,2H), 3.31 (t, J=7.2 Hz, 2H), 2.76 (t, J=7.2 Hz, 2H); ¹³C NMR (1:1CD₃CN/D₂O, 150 MHz): δ 158.08, 157.75, 132.00, 131.09, 115.82, 83.65 (d,J=164.6 Hz), 68.44 (d, J=18.8 Hz), 43.57, 34.36. HRMS calculated forC₁₁H₁₇FN₃O (M+H): 226.1350. Found: 226.1352.

Example 4 Synthesis of4-(4-(2-Fluoroethoxy)phenyl)imidazolidin-2-iminium Chloride

Synthesis of the product of Example 3 also yielded the title compound asa colorless solid (14.2 mg, 27%). ¹H NMR (1:1 CD₃CN/D₂O, 600 MHz): δ7.29-7.26 (m, 2H), 6.98-6.94 (m, 2H), 5.03 (dd, J=7.8, 9.6 Hz, 1H),4.78-4.66 (m, 2H), 4.26-4.18 (m, 2H), 4.00 (t, J=9.6 Hz, 1H), 3.41 (dd,J=7.2, 9.6 Hz, 1H); ¹³C NMR (1:1 CD₃CN/D₂O, 150 MHz): δ 160.52, 159.38,133.73, 128.78, 116.04, 83.59 (d, J=164.7 Hz), 68.47 (d, J=18.8 Hz),58.84, 52.07. HRMS calc'd for C₁₁H₁₅FN₃O (M+H): 224.1194. Found:224.1197.

Example 5 Synthesis of (E)-1-(4-(2-Fluoroethoxy)styryl)guanidiniumChloride

Synthesis of the product of Example 3 also yielded the title compound asa colorless solid (1.2 mg, 2.5%). ¹H NMR (1:1 CD₃CN/D₂O, 600 MHz): δ7.34-7.28 (m, 2H), 6.93-6.87 (m, 3H), 6.23 (d, J=14.4 Hz, 1H), 4.76-4.65(m, 2H), 4.24-4.15 (m, 2H); ¹³C NMR (1:1 CD₃CN/D₂O, 150 MHz): δ 158.70,155.21, 129.52, 128.20, 120.92, 117.08, 116.04, 83.58 (d, J=164.4 Hz),68.46 (d, J=18.9 Hz). MS (ESI): 224.3 (M+H, 100).

Example 6 Synthesis of5-(2-Amino-1-hydroxypropyl)-2-(2-fluoroethoxy)benzene-1,3-diolHydrochloride

Part A—Preparation of Methyl 4-(2-Fluoroethoxy)3,5-dihydroxybenzoate

To a 100 mL round bottom flask was added methyl 3,4,5-trihydroxybenzoate(7.00 g, 88.0 mmol) followed by 25 mL of dimethyl sulfoxide. PotassiumCarbonate (7.88 g, 57.0 mmol), potassium iodide (31.6 mg, 0.19 mmol) and1-bromo-2-fluoroethane (5.79 g, 45.6 mmol) were successively addedfollowed by 25 mL more of dimethyl sulfoxide. The reaction mixture wasstirred for 18 h after which it was diluted by adding water (100 mL).The mixture was poured into a separatory funnel and extracted with DCM(3×40 mL). The organic layer was then washed with water (4×120 mL) andbrine, and dried over magnesium sulfate. The organic layer was thenconcentrated to obtain an oil. The crude oil was purified using silicagel flash chromatography (DCM/ether 39:1) to obtain 1.9 g (22%) of thetitle compound (R_(f)˜0.17 in 19:1 DCM/ether). ¹H NMR (600 MHz, CDCl₃):δ 7.25 (s, 2H), 5.96 (s, 2H), 4.7 (t of d, 2H, J=48, 1.2 Hz), 4.37 (t ofd, 2H, J=24, 1.2 Hz), 3.87 (s, 3H). ¹³C NMR (150 MHz, CDCl₃): δ 166.8,149, 136.8, 126.4, 109.8, 82.16 (d, J=334 Hz), 72.6 (d, J=37.5), 52.3.MS (ESI): 231.4 (M+H, 100); HRMS: Calc'd for C₁₀H₁₁FO₅ (M+H): 231.06633.Found: 231.0664.

Part B—Preparation of Methyl 4-(2-Fluoroethoxy)3,5-bis(methoxymethyloxy)benzoate

A flame dried 100 ml round bottom flask fitted with a reflux condenserwas charged with sodium iodide (3.00 g, 20 mmol) and to this was added1,2-dimethoxyethane (20 mL). Methoxymethyl chloride (2.09 g, 1.97 mL,26.0 mmol) was then added drop-wise to this mixture. A colorlessprecipitate formed. This mixture was stirred for 5 min after which theproduct of Part A (1.5 g, 6.51 mmol) dissolved in dimethoxyethane (20mL) was added to it. Diisopropylethylamine (3.36 g, 4.53 mL, 26.04 mmol)was added to the above mixture and the flask was immersed in an oil bathat 80° C. The resulting mixture was stirred at this temperature for 15 hafter which it was cooled to room temperature. Water (20 mL) was addedand the mixture was extracted with dichloromethane (2×40 mL). Thecombined organic layers were then washed with brine and dried overmagnesium sulfate. Concentration of the organic layer in vacuo gave apale red oil which was subjected to silica gel flash chromatography(hexanes/ether 4:1 to 7:3) to obtain 0.9 g (44%) of the product as aviscous oil. ¹H NMR (600 MHz, CDCl₃): δ 7.5 (s, 2H), 5.25 (s, 4H), 4.7(t ofd, 2H, J=49, 1.2 Hz), 4.3 (d of t, 2H, J=24, 1.2 Hz), 3.88 (s, 3H),3.5 (s, 6H). ¹³C NMR (150 MHz, CDCl₃): δ 166.3, 150.6, 142.9, 125.8,112.1, 95.4, 82.61 (d, J=339 Hz), 72.3 (d, J=40.5 Hz), 56.4, 52.2. HRMS:Calc'd for C₁₄H₁₉FO₇ (M+H): 319.1187. Found: 319.1185.

Part C—Preparation of4-(2-Fluoroethoxy)-3,5-bis(methoxymethyloxy)-benzaldehyde

To a flame dried 50 ml round bottom flask was added a solution of Red-Al(3.29 mL; 65 wt % solution in toluene). Toluene (10 mL) was added to theflask and the solution was cooled to 0° C. in an ice bath. Morpholine(1.01 g, 1.01 mL, 11.6 mmol) was added drop-wise to keep the gasevolution under control. After completion of addition the mixture wasstirred until gas evolution ceased 15-20 min). This solution was addedto a solution of the product of Part B (0.6 g, 1.88 mmol) in toluene (20mL) at −50° C. via a cannula. A precipitate formed in the flask. Themixture was allowed to warm to −30° C. and stirred at this temperaturefor 3 h. Water (15 mL) was added drop-wise to the flask to quench thereaction and the solution was extracted with ether (2×30 mL). Theorganic layer was washed with brine and dried over magnesium sulfate.Concentration in vacuo gave a crude oil which was purified by silica gelflash chromatography (hexanes/ether 3:2 to 1:1) to obtain 420 mg (77%)of the title compound as an oil. ¹H NMR (600 MHz, CDCl₃): δ 9.8 (s, 1H),7.37 (s, 1H), 5.24 (s, 4H), 4.7 (t of d, 2H, J=49, 1.2 Hz), 4.3 (d of t,2H, J=24, 1.2 Hz), 3.51 (s, 6H). ¹³C NMR (150 MHz, CDCl₃): δ 190.7,151.4, 144.2, 132.3, 111.9, 104.2, 95.5, 82.61 (d, J=169 Hz), 72.3 (d,J=20.1 Hz), 56.4. HRMS: Calculated for C₁₃H₁₇FO₆ (M+H): 218.1081. Found:289.1082.

Part D—Preparation of1-(4-(2-Fluoroethoxy)-3,5-bis(methoxymethoxy)-phenyl)-2-nitropropan-1-ol

A flame dried 15 mL round bottom flask was charged with product fromPart C (270 mg, 0.93 mmol) and to this was added nitroethane (5 mL) andthe solution was cooled to 0° C. Tetramethylguanidine (4 drops asmeasured by a Pasteur pipette) was added to the above mixture and thecontents were stirred for 90 min. The mixture was poured into aseparatory funnel containing water (5 mL) and extracted with ethylacetate (2×15 mL). The organic layer was washed with brine and driedover magnesium sulfate. Concentration in vacuo gave a crude oil whichwas purified by silica gel flash chromatography (hexanes/ether 3:2) toobtain 130 mg (18%) of the title compound as an oil in a 3:1 (A:B)mixture of diastereomers. The OH proton in pair B and both the CHNO₂protons in pair A were heavily overlaid with other signals causingambiguity and are hence not reported. Pair A: ¹H NMR (600 MHz, CDCl₃): δ6.85 (s, 2H), 5.2 (s, 4H), 4.92 (d of d, 1H, J=4.2, 9 Hz), 4.7 (d of t,2H, J=49, 1.2 Hz), 4.25 (d of t, 2H, J=24, 1.2 Hz), 3.5 (s, 6H), 2.5 (d,1H, J=4.2 Hz), 1.35 (d, 3H, J=6.6 Hz). ¹³C NMR (150 MHz, CDCl₃): δ151.4, 139.4, 134.3, 109.6, 95.6, 88.2, 82.64 (d, J=169 Hz), 76, 73.5,72.3 (d, J=21 Hz), 56.3, 15.3. Pair B: ¹H NMR (600 MHz, CDCl₃): δ 6.85(s, 4H), 5.2 (s, 8H), 4.7 (d of t, 2H, J=49, 1.2 Hz), 4.25 (d of t, 2H,J=24, 1.2 Hz), 3.5 (s, 6H), 2.6 (d, 1H, J=3.6 Hz), 1.5 (d, 3H, J=7.2Hz). ¹³C NMR (150 MHz, CDCl₃): δ 151.2, 138.9, 134.6, 108.8, 95.6, 87.2,82.64 (d, J=169 Hz), 76, 73.5, 72.3 (d, J=21 Hz), 56.3, 12.2. HRMS:Calc'd for C₁₅H₂₂FNO₈ (M+Na): 386.1221. Found: 386.1220.

Part E—Preparation of1-(4-(2-Fluoroethoxy)-3,5-bis(methoxymethoxy)phenyl)-1-hydroxypropan-2-aminiumTrifluoroacetate

The product of Part D (53 mg, 0.145 mmol) was charged to a flame dried10 mL flask followed by methanol (1 mL). The flask was evacuated twicefollowed by purging with nitrogen. Pd—C (10 mg, 10 wt %) was added inone lot and the flask fitted with a hydrogen balloon. After stirring forone hour, ammonium formate (91 mg, 1.45 mmol) was added to the reactionfollowed by methanol (1 mL). The mixture was heated to reflux for 1 hand cooled to room temperature. The reaction mixture was filteredthrough a pad of Celite® and concentrated in vacuo to obtain a colorlesssolid. This crude solid was dissolved in water and subjected topreparative HPLC purification (Phenomenex Luna C18(2) column 10μ,21.2×250 mm; gradient: 0-90% B over 30 min at 20 mL/min; Mobile phaseA=0.1% TFA in water and B=0.1% TFA in 90% water) to obtain 10 mg (20%)of the title compound as a thick oil and as a diastereomeric mixtureindistinguishable by NMR. ¹H NMR (600 MHz, CD₃OD): δ 6.9 (s, 2H), 5.2(s, 4H), 4.7 (d of t, 2H, J=49, 1.2 Hz), 4.25 (d of t, 2H, J=24, 1.2Hz), 3.5 (s, 6H), 3.35 (m, 1H), 1.0 (d, 3H, J=6.6 Hz). ¹³C NMR (150 MHz,CD₃OD): δ 152.5, 140.6, 138.2, 110.8, 96.9, 84.1 (d, J=167 Hz), 76, 73.8(d, J=21 Hz), 56.8, 54.6, 15.8. HRMS: Calc'd for C₁₅H₂₄FNO₆ (M+H):334.1660. Found: 336.1662.

Part F—Preparation of5-(2-Amino-1-hydroxypropyl)-2-(2-fluoroethoxy)-benzene-1,3-diolHydrochloride

To a flame dried 5 mL flask was added product of Part E (6 mg, 0.018mmol) followed by methanol (1 mL). To this solution was added 2-3 dropsof concentrated HCl and the solution was heated to reflux for 30 min.All solvent was removed in vacuo to obtain 3 mg (68%) of the titlecompound as a thick oil and as a mixture of diastereomersindistinguishable by NMR. ¹H NMR (600 MHz, CD₃OD): δ 6.49 (s, 2H), 4.7(d of t, 2H, J=49, 1.2 Hz), 4.31 (d, 1H, J=8.4 Hz), 4.25 (d of t, 2H,J=24, 1.2 Hz), 3.45 (m, 1H), 1.5 (m, 3H). HRMS: Calc'd for C₁₁H₁₆FNO₄(M+H): 246.1136. Found: 246.1134.

Example 7 Synthesis of 3-Methoxy-4-fluorobenzylguanidinium Chloride

Part A—Preparation of 3-Methoxy-4-fluorobenzylamine

A flame dried 50 mL round bottom flask was charged with lithium aluminumhydride (0.63 g, 16.6 mmol) and to this was added tetrahydrofuran (25mL). The solution was cooled to 0° C. and 3-methoxy-4-fluorobenzonitrile(1.0 g, 6.62 mmol) was added in one portion. The ice bath was removedafter an hour and the resulting mixture was stirred for 16 h after whichit was cooled to 0° C. and quenched by adding 0.63 mL water, 0.63 mL 15%NaOH and 1.89 mL water drop-wise and in succession. The mixture wasstirred for 20 min and filtered. The filtrate was concentrated in vacuoto obtain 890 mg (86%) of the title compound as an oil. NMR indicated nofurther purification was required. ¹H NMR (300 MHz, DMSO-d₆): δ 7.1 (m,2H), 6.85 (m, 1H), 3.84 (s, 3H), 3.7 (s, 2H). ¹³C NMR (75 MHz, DMSO-d₆):δ 150.0 (d, J=240 Hz), 146.6 (d, J=10.5 Hz), 141.1 (d, J=3.75 Hz),118.75 (d, J=6.75 Hz), 115.1 (d, J=18 Hz), 112.5, 55.75, 45.2. HRMS:Calc'd for C₈H₁₀FNO (M+H): 156.0819. Found: 156.0818.

Part B—Preparation of3-Methoxy-4-fluorobenzyl-bis(tert-butoxycarbonyl)-guanidine

To a 10 mL flame dried flask was added the product of Part A (0.1 g,0.644 mmol) and this was dissolved in MeCN.N,N-bis(tert-butoxycarbonyl)-1H-pyrazole-1-carboxamidine (0.2 g, 0.64mmol) was added to the above solution and this was stirred for 30 minafter which it was concentrated in vacuo to obtain a oil. This oil waspurified by silica gel flash chromatography (dichloromethane) to obtain0.22 g (86%) of the title compound as a colorless solid. ¹H NMR (600MHz, DMSO-d₆): δ 11.46 (s, 1H), 8.65 (t, 1H, J=5.4 Hz), 7.22 (d of d,1H, J=8.4, 2.4 Hz), 7.15 (d of t, 1H, J=8.4, 3 Hz), 6.85 (m, 1H), 4.45(d, 2H, J=6 Hz), 3.82 (s, 3H), 1.47 (s, 9H), 1.38 (s, 9H). ¹³C NMR (150MHz, DMSO-d₆): δ 162.8, 155.1, 151.8, 149.8, 146.7 (d, J=10.6 Hz),134.9, 119.5, 115.4 (d, J=18 Hz), 113.7, 82.8, 78.1, 55.7, 43.1, 27.8,27.5. HRMS: Calc'd for C₁₉H₂₈FN₃O₅ (M+H): 398.2085. Found: 398.2084.

Part C—Preparation of Preparation of 3-Methoxy-4-fluorobenzylguanidiniumChloride

The product of Part B (0.06 g, 0.151 mmol) was charged to a 5 mL flamedried flask and to this was added dioxane (2 mL). Concentratedhydrochloric acid (0.5 mL) was added to the mixture and the solution wasstirred at room temperature for 24 h. The reaction mixture wasconcentrated in vacuo, redissolved in 2 mL MeCN/water (1:1) mixture andlyophilized to obtain 35 mg (100%) of the product as the hydrochloridesalt. ¹H NMR (300 MHz, DMSO-d₆): δ 8.26 (t, 1H, J=6 Hz), 7.2 (m, 2H),6.88 (m, 1H), 4.34 (d, 2H, J=6.6 Hz), 3.84 (s, 3H). ¹³C NMR (75 MHz,DMSO-d₆): δ 157, 152.4, 149.1, 147 (d, J=10.5 Hz), 133.9, 119.4 (d,J=6.75 Hz), 115.7 (d, J=18 Hz), 113.2, 55.9, 43.5. HRMS: Calc'd forC₉H₁₂FN₃O (M+H): 198.1037. Found: 198.1037.

Example 8 Synthesis of 3-Bromo-4-(2-fluoroethoxy)benzylguanidiniumChloride

Part A—Preparation of 3-Bromo-4-(2-fluoroethoxy)benzonitrile

To a flame dried 50 mL round bottom flask was added3-bromo-4-hydroxybenzonitrile (1.0 g, 5.05 mmol) followed by 5 mL ofdimethyl sulfoxide. Potassium iodide (4.2 mg, 0.025 mmol) and potassiumcarbonate (1.05 g, 7.58 mmol) were added. The flask was immersed in anoil bath at 85° C. and 1-bromo-2-fluoroethane (0.769 g, 0.45 mL, 6.06mmol) was added. The reaction was stirred at this temperature for 1 hafter which it was cooled to room temperature and diluted with water (10mL). The resulting solution was extracted with dichloromethane (2×20mL). The organic layer was then washed with water (3×20 mL) and brine,and dried over magnesium sulfate. The solution was filtered andconcentrated in vacuo to obtain an oil which was purified by silica gelflash chromatography using dichloromethane. Product (1.13 g, 92%) wasobtained as a colorless solid. ¹H NMR (600 MHz, CDCl₃): δ 7.83 (s, 1H),7.57 (d of d, 1H, J=8.4, 1.8 Hz), 6.94 (d, 1H, J=8.4 Hz), 4.8 (t of d,2H, J=49, 1.2 Hz), 4.35 (t of d, 2H, J=24, 1.2 Hz). ¹¹C NMR (150 MHz,CDCl₃): δ 158.5, 136.9, 132.9, 117.5, 113, 106, 81.5 (d, J=171 Hz), 68.5(d, J=21 Hz). HRMS: Calc'd for C₉H₇BrFNO (M+H): 243.9767. Found:243.9767.

Part B—Preparation of 3-Bromo-4-(2-fluorethoxy)benzylammonium Formate

NiCl₂.6H₂O (180 mg, 0.758 mmol) was dried in a vacuum oven at 150° C.for 16 h to make anhydrous NiCl₂. This dried NiCl₂ was then charged to aflame-dried 15 mL two necked round bottom flask fitted with a refluxcondenser. Anhydrous ethanol (2 mL) was added to the flask followed bythe product from Part A (184 mg, 0.758 mmol) followed by sodiumborohydride (86 mg, 2.27 mmol). Gas evolution was seen when sodiumborohydride was added. After 90 min additional sodium borohydride (43mg, 1.14 mmol) was added and the reaction mixture was stirred for anadditional 10 min. The reaction mixture was filtered through a 0.2syringe filter, diluted with water (2.0 mL) and extracted with ethylacetate (3×8 mL). The combined organic layers were washed with brine anddried over magnesium sulfate. The crude product obtained afterconcentration of the organic layer in vacuo was subjected topurification via preparative HPLC ((Phenomenex Luna C18(2) column 10μ,21.2×250 mm; Mobile phase A=0.1% Formic acid in water and B=0.1% formicacid in 90% water at 20 mL/min) to obtain 38 mg (20%) of the product asthe formate salt. ¹H NMR (600 MHz, DMSO-d₆): δ 8.4 (s, 2H), 7.6 (s, 1H),7.3 (m, 1H), 7.1 (m, 1H), 4.8 (d of t, 2H, J=48, 1.2 Hz), 4.3 (d of t,2H, J=24, 1.2 Hz), 3.7 (m, 2H). HRMS: Calc'd for C₉H₉BrFO (M+H—NH₃):230.9820. Found: 230.9821.

Part C—Preparation of3-Bromo-4-(2-fluoroethoxy)benzyl-bis(tert-butoxycarbonyl)guanidine

To a flame dried 10 mL round bottom flask was charged the product ofPart B (30 mg, 0.102 mmol) and this was dissolved in MeCN (1.5 mL).Diisopropylethylamine (26.4 mg, 0.204 mmol) was then added to itfollowed by N,N-bis(tert-butoxycarbonyl)-1H-pyrazole-1-carboxamidine(31.7 mg, 0.102 mmol). The reaction mixture was stirred for 1 h afterwhich it was concentrated and purified by silica gel flashchromatography using dichloromethane as eluant. The product (29 mg, 58%)was obtained as a sticky solid. ¹H NMR (600 MHz, DMSO-d₆): δ 11.4 (s,1H), 8.65 (t, 1H, J=6, 5.4 Hz), 7.58 (s, 1H), 7.28 (d of d, 1H, J=8.4,1.8 Hz), 7.1 (d, 1H), 4.75 (d of t, 2H, J=48, 5.4, 1.2 Hz), 4.45 (d, 2H,J=6 Hz), 4.3 (d of t, 2H, J=24, 1.2 Hz), 1.47 (s, 9H), 1.39 (s, 9H). ¹³CNMR (150 MHz, CDCl₃): δ 162.8, 155.1, 153.5, 151.1, 132.3, 128.1, 113.9,110.7, 82.8, 81.88 (d, J=166 Hz), 78.1, 68.25 (d, J=3.9 Hz), 42.3, 27.8,27.5. HRMS: Calc'd for C₂₀H₂₉BrFN₃O₅ (M+H): 490.1347. Found: 490.1349.

Part D—Preparation of 3-Bromo-4-(2-fluoroethoxy)benzylguanidiniumChloride

The product of Part C (23 mg, 0.046 mmol) was charged to a flame dried10 mL round bottom flask and dissolved in dioxane (1.0 mL). Concentratedhydrochloric acid (1.0 mL) was added and the reaction was stirred for 16h at ambient temperature. The reaction mixture was concentrated invacuo, redissolved in 2 mL of MeCN/water (1:1), and lyophilized toobtain 15 mg (88%) of the product as the hydrochloride salt. ¹H NMR (600MHz, DMSO-d₆): δ 8.12 (t, 1H, J=6 Hz), 7.56 (d, 1H, J=2.4 Hz), 7.29 (dof d, 1H, J=8.7, 2.4 Hz), 7.15 (d, 1H, J=8.4 Hz), 4.75 (t of d, 2H,J=47.4, 4.2 Hz), 4.32 (t of d, J=30, 3.6 Hz), 4.31 (d, 2H, J=6.6 Hz).¹³C NMR (150 MHz, CDCl₃): δ 158.8, 153.7, 131.9, 131.3, 127.9, 113.9,110.9, 81.8 (d, J=166 Hz), 68.3 (d, J=18.9 Hz), 42.6. HRMS: Calc'd forC₁₀H₁₃BrFN₃O (M+H): 290.0298. Found: 290.0298.

Example 9 Synthesis of 3-(2-Fluoroethoxy)benzylguanidiniumTrifluoroacetate

Part A—Preparation of 3-(2-Fluoroethoxy)benzonitrile

To a flame dried 50 mL round bottom flask was added 3-cyanophenol (1.0g, 8.39 mmol) followed by 10 mL dimethyl sulfoxide. Potassium iodide(7.0 mg, 0.042 mmol) and potassium carbonate (1.74 g, 12.6 mmol) wereadded. The flask was immersed in an oil bath at 85° C. and1-bromo-2-fluoroethane (1.17 g, 0.686 mL, 9.23 mmol) was added. Thereaction was stirred at this temperature for 30 min, cooled to roomtemperature, filtered, and the filtrate was diluted with water (100 mL).The resulting solution was extracted with dichloromethane (3×30 mL). Theorganic layer was then washed with water (5×20 mL) and brine, and driedover magnesium sulfate. The solution was filtered and concentrated invacuo to obtain 1.31 g (94%) of an oil as the product. ¹H NMR (600 MHz,CDCl₃): δ 7.37 (m, 1H), 7.26 (m, 1H), 7.15 (m, 2H), 4.75 (t of d, 2H,J=4.2, 46.8 Hz), 4.22 (t of d, 2H, J=4.2, 27.6 Hz). ¹³C NMR (75 MHz,CDCl₃): δ 158.4, 130.4, 125, 119.8, 117.9, 117.5, 113.3, 81 (d, J=171Hz), 67.4 (d, J=10.1 Hz).

Part B—Preparation of 3-(2-Fluoroethoxy)benzylamine

Lithium aluminum hydride (0.67 g, 17.9 mmol) was charged to a flamedried 50 mL round bottom flask and the flask was cooled to 0° C.Tetrahydrofuran (14 mL) was added to the flask, followed by the productof Part A (1.18 g, 7.14 mmol). The ice bath was removed and the mixturestirred for 1.5 h, cooled to 0° C., and quenched by adding water (0.68mL) and 15% NaOH (0.68 mL), followed by an addition of water (2.04 mL).This mixture was stirred for 20 min, filtered, and the filtrate wasconcentrated to afford 1.22 g (100%) of the product as an oil. This oilwas pure by NMR. ¹H NMR (300 MHz, CDCl₃): δ 7.25 (m, 1H), 6.9 (m, 2H),6.8 (m, 1H), 4.75 (t of d, 2H, J=4.2, 47 Hz), 4.25 (t of d, 2H, J=4.2,28 Hz), 3.8 (s, 2H). ¹³C NMR (75 MHz, CDCl₃): δ 158.6, 145.1, 129.5,119.9, 113.3, 112.8, 81.9 (d, J=169 Hz), 67 (d, J=21 Hz), 46.3.

Part C—Preparation of 3-(2-Fluoroethoxy)benzylbis(tert-butoxycarbonyl)guanidine

A 15 mL round bottom flask was flame dried and charged with the productof Part B (0.1 g, 0.59 mmol) and this was dissolved in MeCN (3.5 mL).N,N-bis(tert-butoxycarbonyl)-1H-pyrazole-1-carboxamidine (0.183 g, 0.591mmol) was added, the solution was stirred for 90 min, and concentratedin vacuo to a oil. This crude oil was purified by silica gel flashchromatography using dichloromethane as eluant to give 199 mg (92%) ofthe product as a oil. ¹H NMR (300 MHz, CDCl₃): δ 11.5 (br t, 1H), 8.4(br t, 1H), 7.24 (d, 2H, J=9 Hz), 6.88 (d, 2H, J=9 Hz), 4.73 (t of d,2H, J=6, 48 Hz), 4.54 (d, 2H, J=6 Hz), 4.2 (t of d, 2H, J=3, 27 Hz), 1.5(s, 9H), 1.46 (s, 9H). ¹³C NMR (75 MHz, CDCl₃): δ 163.6, 157.9, 155.9,153.1, 130, 129.2, 114.9, 83.1, 81.1 (d, J=169 Hz), 79.3, 67.1 (d, J=20Hz), 44.4, 28.3, 28.

Part D—Preparation of 3-(2-Fluoroethoxy)benzylguanidiniumTrifluoroacetate

The product of Part C (95 mg, 0.231 mmol) was charged to a flame dried15 mL flask and dissolved in dioxane (0.5 mL). A solution of 4M HCl indioxane (2.5 mL) was added followed by concentrated hydrochloric acid(0.5 mL). The reaction mixture was stirred for 16 h, and concentrated invacuo to obtain a oil. This oil was purified by preparative HPLC(Phenomenex Luna C18(2) column 10 21.2×250 mm; gradient: 0% B for 5 minthen 0-30% B over 20 min at 20 mL/min; Mobile phase A=0.1% TFA in waterand B=0.1% TFA in 90% water) to obtain 34 mg (52%) of the titlecompound. ¹H NMR (600 MHz, CDCl₃+3 drops DMSO-d₆): δ 8.0 (t, 1H, J=6Hz), 7.1 (t, 1H, J=7.8 Hz), 6.85 (m, 2H), 6.76 (1H, d of d, J=8.4, 1.8Hz), 4.67 (t of d, 2H, J=4.2, 47.4 Hz), 4.31 (d, 2H, J=6 Hz), 4.16 (t ofd, 2H, J=4.2, 28.8 Hz). HRMS: Calc'd for C₁₀H₁₄FN₃O (M+H): 212.1193.Found: 212.1191.

Example 10 Synthesis of 3-Chloro-4-(2-fluoroethoxy)phenethylguanidiniumTrifluoroacetate

Part A—Preparation of 3-Chloro-4-hydroxyphenethylammoniumTrifluoroacetate

To a 25 mL round bottom flask was added 3-chloro-4-methoxyphenethylamine hydrochloride and this was dissolved in hydrobromic acid(6.8 mL). The solution was heated to 110° C. for 5 h after which it wasconcentrated and dissolved in water (5 mL). The aqueous solution waspurified by preparative HPLC (Phenomenex Luna C18(2) column 10μ,21.2×250 mm; gradient: 0% B for 10 min then 0-30% B over 30 min at 20mL/min; Mobile phase A=0.1% TFA in water and B=0.1% TFA in 90% water) toobtain 289 mg (51%) of the title compound. ¹H NMR (600 MHz, DMSO-d₆): δ10.1 (s, 1H), 7.8 (br, 3H), 7.23 (s, 1H), 7.01 (1H, d, J=8.4 Hz), 6.92(d, 1H, J=8.4 Hz).

Part B—Preparation ofN-(tert-Butoxycarbonyl)-3-chloro-4-hydroxyphenethylamine

To a flame dried 15 mL round bottom flask was added the product of PartA (97 mg, 0.34 mmol), followed by a mixture of dimethylformamide anddichloromethane (4 mL; 1:1) to dissolve it. Diisopropylethylaminc (87.9mg, 0.118 mL, 0.68 mmol) and di-tert-butyl dicarbonate (89 mg, 0.408mmol) were then added successively and the mixture was stirred for 30min. The reaction mixture was concentrated in vacuo and the crude oilsubjected to silica gel flash chromatography in dichloromethane to give72 mg (78%) of the product. ¹H NMR (600 MHz, DMSO-d₆): δ 9.85 (s, 1H),7.12 (s, 1H), 6.93 (d, 1H, J=8.4 Hz), 6.86 (m, 1H), 6.79 (br t, 1H),3.075 (q, 2H, J=6.6 Hz), 2.57 (t, 2H, J=7.2 Hz), 1.35 (s, 9H).

Part C—Preparation of 3-Chloro-4-(2-fluoroethoxy)phenethylammoniumTrifluoroacetate

Powdered sodium hydroxide (14.2 mg, 0.356 mmol) was placed in a 15 mLround bottom flask. The product of Part B (69 mg, 0.254 mmol) was addedfollowed by dimethylsulfoxide (2.5 mL). The resulting mixture wasstirred for 5 min after which 1-p-tosyloxy-2-fluoroethane (preparedaccording to literature reference: J. Med. Chem. 1980, 23, 985-990) wasadded, and the flask immersed in a preheated oil bath at 75° C. Thereaction was stirred for 60 min after which it was cooled to roomtemperature and diluted with dichloromethane (10 mL). The organic layerwashed with water (5×6 mL) and brine, dried over magnesium sulfate, andconcentrated in vacuo to give 120 mg of an oil. This oil was added asolution of trifluoroacetic acid in dichloromethane (3.0 mL, 1:1) andthe resulting solution was stirred for 60 min at ambient temperature.The reaction mixture was concentrated in vacuo and subjected topreparative HPLC (Phenomenex Luna C18(2) column 10μ, 21.2×250 mm;gradient: 10-40% B over 20 min at 20 mL/min; Mobile phase A=0.1% TFA inwater and B=0.1% TFA in 90% water) to obtain 52 mg (62% for two steps)of the title compound. ¹H NMR (600 MHz, DMSO-d₆): δ 7.8 (br, 2H), 7.36(d, 1H, J=1.8 Hz), 7.19 (d of d, 1H, J=2.4, 8.4 Hz), 7.13 (d, 1H, J=8.4Hz), 4.75 (t of d, 2H, J=4.2, 41.4 Hz), 4.32 (t of d, 2H, J=3.6, 32 Hz),3.0 (br t, 2H), 2.8 (t, 2H, J=7.8 Hz). ¹³C NMR (150 MHz, DMSO-d₆): δ152.3, 130.9, 130.1, 128.5, 121.4, 114.2, 81.9 (d, J=166 Hz), 68.2 (d,J=18.9 Hz). HRMS: Calc'd for C₁₀H₁₃FClNO (M+H): 218.0742. Found:218.0743.

Part D—Preparation of 3-Chloro-4-(2-fluoroethoxy)phenethylguanidiniumTrifluoroacetate

To a flame dried 5 mL, flask was added product of Part C (47 mg, 0.142mmol). To this was added MeCN (1.4 mL) and diisopropylethylamine (37 mg,50 μL, 0.248 mmol), followed byN,N-bis(tert-butoxycarbonyl)-1H-pyrazole-1-carboxamidine (44 mg, 0.142mmol). The solution was stirred for 90 min after which it wasconcentrated in vacuo to an oil. This oil was passed through a plug ofsilica gel and eluted with hexanes/DCM (1:1 to 1:2). The eluant wasconcentrated to obtain 64 mg (98%) of an oil. This oil was redissolvedin trifluoroacetic acid (1 mL) and heated to 55° C. for 5 min afterwhich it was concentrated and purified by preparative HPLC (PhenomenexLuna C18(2) column 10μ, 21.2×250 mm; gradient: 10-40% B over 20 min at20 mL/min; Mobile phase A=0.1% TFA in water and B=0.1% TFA in 90% water)to obtain 37 mg (54% for last step) of the title compound. ¹H NMR (600MHz, DMSO-d₆): δ 7.56 (br t, 1H), 7.38 (d, 1H, J=2.4 Hz), 7.185 (d of d,1H, J=2.4, 8.4 Hz), 7.15 (d, 1H, J=8.4 Hz), 4.75 (t of d, 2H, J=4.2, 48Hz), 4.3 (t of d, 2H, J=3.6, 30 Hz), 3.6 (br, 2H), 3.33 (AB q, 2H, J=6.6Hz), 2.72 (t, 2H, J=7.8 Hz). ¹³C NMR (150 MHz, DMSO-d₆): δ 156.6, 152.1,132, 130.2, 128.5, 121.2, 117.9, 114, 81.9 (d, J=165.9 Hz), 68.21 (d,J=18.75 Hz), 41.8, 33.1. HRMS: Calc'd for C₁₁H₁₅ClFN₃O (M+H): 260.0960.Found: 260.0962.

Example 11 Synthesis of1-(4-Fluoro-3-hydroxyphenyl)-1-hydroxy-N-methylpropan-2-aminiumTrifluoroacetate

Part A—Preparation of 1-(4-Fluoro-3-methoxyphenyl)-2-nitropropan-1-ol

To a flame dried 100 mL round bottom flask was added3-methoxy-4-fluorobenzaldehyde (367 mg, 2.38 mmol) and this wasdissolved in methanol (23 mL). The reaction solution was cooled to 0° C.and nitroethane (357 mg, 4.76 mmol) was added to it followed by 5M NaOH(0.476 mL, 2.38 mmol). The solution was stirred for 80 min at 0° C.after which acetic acid (2% solution, 32 mL) was added and stirred foran additional 30 min. The reaction mixture was concentrated and water(10 mL) was added. The solution was extracted with dichloromethane (4×20mL). The combined organic layers were washed with brine, dried overmagnesium sulfate, and concentration to give afford an oil which waspurified by silica gel flash chromatography using dichloromethane aseluant. Product (391 mg, 72%) product was obtained as a colorless oil ina 1.88:1 ratio (A:B) of diastereomers. Pair A: ¹H NMR (600 MHz, CDCl₃):δ 7.07 (m, 1H), 7.0 (m, 1H), 6.8 (m, 1H), 5.34 (t, 1H, J=3 Hz), 4.65 (dof q, 1H, J=3.6, 6.6 Hz), 3.9 (s, 3H), 2.697 (d, 1H, J=3.6 Hz), 1.5 (d,3H, J=6.6 Hz). ¹³C NMR (75 MHz, CDCl₃): δ 153.3, 150.1, 147.44 (d,J=10.8 Hz), 134.1, 117.7 (d, J=7 Hz), 115.7 (d, J=18.6 Hz), 110.6, 86.8,72.8, 55.8, 11.7. Pair B: ¹H NMR (600 MHz, CDCl₃): δ 7.07 (m, 1H), 7.0(m, 1H), 6.8 (m, 1H), 4.9 (d of d, 1H, J=3.6, 9 Hz), 4.72 (m, 1H), 3.9(s, 3H), 2.57 (d, 1H, J=4.2 Hz), 1.33 (d, 3H, J=5.4 Hz). ¹³C NMR (75MHz, CDCl₃): δ 153.8, 150.5, 147.76 (d, J=10.8 Hz), 134.1, 119 (d, J=7Hz), 115.8 (d, J=18.6 Hz), 111, 87.7, 75.3, 55.8, 15.9. HRMS: Calc'd forC₁₀H₁₂FNO₄ (M+Na): 252.0642. Found: 252.0643.

Part B—Preparation of 1-(4-Fluoro-3-methoxyphenyl)-2-aminopropan-1-ol

The product of Part A (301 mg, 1.31 mmol) was dissolved in a mixture oftetrahydrofuran and methanol (13 mL, 1:1) in a 50 mL flame dried roundbottom flask. To this solution was added Pd—C (10 wt %, 69.7 mg, 0.065mmol) followed by ammonium formate (413 mg, 6.55 mmol). The reactionsolution was stirred at ambient temperature for 20 h after which anadditional 413 mg ammonium formate and 70 mg Pd—C catalyst were added.The reaction mixture was stirred an additional 3 h after which it wasfiltered through a pad of Celite® and the filtrate concentrated in vacuoto obtain an oil. This oil was subjected to silica gel flashchromatography (DCM/MeOH/aqueous ammonia 8.9:1:0.1) to obtain 115 mg(44%) of the product as an oil in a 2:1 (A:B) mixture of diastereomers.Pair A: ¹H NMR (600 MHz, DMSO-d₆): δ 7.0 (m, 2H), 6.84 (m, 1H), 4.1 (d,1H, J=6.6 Hz), 3.82 (s, 3H), 2.79 (dddd, 1H, J=6.6 Hz), 0.79 (d, 3H,J=6.6 Hz). ¹³C NMR (150 MHz, CDCl₃): δ 151.2, 149.6, 146.4, 140.7,118.65, 114.75, 112, 77.8, 55.8, 52.6, 19.3. Pair B: ¹H NMR (600 MHz,DMSO-d₆): δ 7.0 (m, 2H), 6.84 (m, 1H), 4.28 (d, 1H, J=6.6 Hz), 3.82 (s,3H), 2.87 (dddd, 1H, J=6.6 Hz), 0.85 (d, 3H, J=6.6 Hz). ¹³C NMR (150MHz, CDCl₃): δ 151.2, 149.6, 146.4, 140.3, 118.65, 114.75, 112, 77.0,55.8, 52.1, 18.1. HRMS: Calc'd for C₁₀H₁₄FNO₂ (M+H): 200.1081. Found:200.1078.

Part C—Preparation of1-(4-Fluoro-3-methoxyphenyl)-2-(methylamino)propan-1-ol

The product of Part B (101 mg, 0.507 mmol) was dissolved in ethylformate (10 mL) in a flame dried 50 mL round bottom flask fitted with areflux condenser. The solution was heated at 60° C. for 16 h,concentrated in vacuo, and the crude oil obtained was purified by silicagel flash chromatography (dichloromethane/methanol/ammonia 8.9:1:0.1) toyield 101 mg of the intermediate aldehyde. This aldehyde (50 mg, 0.22mmol) was dissolved in tetrahydrofuran (5.0 mL) and added drop-wise to asolution of lithium aluminum hydride in tetrahydrofuran (1.27 mL of a1.0M solution) at 0° C. The reaction was stirred at 0° C. for 30 minafter which the bath was removed and the solution stirred at ambienttemperature for 30 min and at reflux for 30 min. The reaction was thenquenched by adding 59 μL water, 59 μL, 15% NaOH and finally 0.2 mLwater. The suspension was stirred for 20 min, filtered, and concentratedto an oil. This oil was subjected to purification using silica gel flashchromatography (dichloromethane/methanol/ammonia 8.9:1:0.1) to yield 38mg (81%) of product as a 2.5:1 (A:B) mixture of diastereomers. Pair A:¹H NMR (300 MHz, DMSO-d₆): δ 7.11 (m, 2H), 6.85 (m, 1H), 4.21 (d, 1H,J=9 Hz), 3.83 (s, 3H), 2.57 (m, 1H), 2.29 (s, 3H), 0.71 (d, 3H, J=6 Hz).¹³C NMR (75 MHz, DMSO-d₆): δ 152.1, 148.8, 146.47, 140.37 (d, J=3 Hz),119.17 (d, J=6.75 Hz), 114.87, 112.2, 75.6, 60.5, 55.8, 33.3, 15.1. PairB: ¹H NMR (300 MHz, DMSO-d₆): δ 7.11 (m, 2H), 6.85 (m, 1H), 4.57 (d, 1H,J=6 Hz), 3.83 (s, 3H), 2.62 (m, 1H), 2.29 (s, 3H), 0.79 (d, 3H, J=6 Hz).¹³C NMR (75 MHz, DMSO-d₆): δ 151.7, 148.5, 146.47, 140.6 (d, J=3 Hz),118.29 (d, J=6.75 Hz), 114.87, 111.68, 72.7, 60.0, 55.8, 33.3, 13.95.HRMS: Calc'd for C₁₁H₁₆FNO₂ (M+H): 214.1237. Found: 214.1239.

Part D—Preparation of1-(4-Fluoro-3-hydroxyphenyl)-1-hydroxy-N-methylpropan-2-aminiumTrifluoroacetate

To a flame dried 15 mL round bottom flask was added the product of PartC (30 mg, 0.141 mmol) and this was dissolved in dichloromethane (2.0mL). The contents were cooled to −78° C. and a solution of borontribromide (0.353 mL, 1.0 M in DCM) was added drop-wise. The reactionmixture was stirred for 5 h after which it poured into a beakercontaining cold water (2 mL) and stirred for another 1 hr. This mixturewas then poured into a separatory funnel and the layers separated. Theorganic layer was washed with saturated sodium bicarbonate and extractedwith 2M NaOH (3×5 mL). The combined NaOH solution was then acidified topH 3 using 5N HCl and extracted with dichloromethane (3×10 mL). Theaqueous layer was lyophilized to obtain a solid which was trituratedwith a MeCN/water mixture (10 mL, 1:1). This mixture was subjected topreparative HPLC ((Phenomenex Luna C18(2) column 10μ, 21.2×250 mm;gradient: 10% B for 10 min the 10-30% B over 20 min at 20 mL/min; Mobilephase A=0.1% TFA in water and B=0.1% TFA in 90% water) to obtain 20 mg(45%) of the title compound as a 2:1 (A:B) mixture of diastereomers.Pair A: ¹H NMR (600 MHz, DMSO-d₆): δ 9.99 (s, 1H), 8.52 (br, 1H), 7.13(m, 1H), 6.9 (m, 1H), 6.77 (m, 1H), 6.3 (d, 1H, J=3.6 Hz), 4.4 (d, 1H,J=6 Hz), 3.3 (br, 1H), 2.5 (s, 3H), 0.95 (d, 3H, J=6.6 Hz). ¹³C NMR (150MHz, DMSO-d₆): δ 149.9, 144.75 (d, J=12.3 Hz), 137.5, 117.8, 116.2,115.5, 72.6, 58, 48, 29, 11.9. Pair B: ¹H NMR (600 MHz, DMSO-d₆): δ 9.90(s, 1H), 8.38 (br, 1H), 7.13 (m, 1H), 6.9 (m, 1H), 6.77 (m, 1H), 6.1 (d,1H, J=3.6 Hz), 4.9 (br t, 1H), 3.21 (br t, 1H), 2.59 (s, 3H), 0.91 (d,3H, J=6.6 Hz). ¹³C NMR (150 MHz, DMSO-d₆): δ 149.3, 144.5 (d, J=12.3Hz), 137.3, 116.4, 116.2, 115.5, 69, 58, 48, 30.4, 9.1. HRMS: Calc'd forC₁₀H₁₄FNO₂ (M+H): 200.1081. Found: 200.1081.

Example 12 Norepinephrine Transporter Binding Assay

Inhibitors to be tested were dissolved in incubation buffer (50 mMTris-HCl, 10% sucrose, pH 7.4) at appropriate dilutions. The inhibitorsolutions were added to the wells of a microtiter plate (40 μL/well) intriplicate. Each well of test agent (and appropriate control wells) wastreated with a mixture of MDCK cell membrane preparation (22.4 μg ofmembrane) expressing human norepinephrine transporter (Bmax=3.7 pmolnorepinephrine transporter/mg protein), and [³H]desipramine (2 nM, 64.8Ci/mmol) in a total volume of 0.2 mL. The resulting mixtures wereincubated for 2 h on ice. A 96 well GF/C filter plate was presoaked withcoating buffer (0.5% polyvinylpyrrolidine and 0.1% Tween 20) for 2 h atroom temperature. The presoaked filter plate was washed with incubationbuffer (6×0.2 mL). The NET reactions were transferred to the coatedfilter plate and filtered. The filter plate was washed (6×0.2 mL) withice cold wash buffer (50 mM Tris-HCl, 0.9% NaCl, pH 7.4). The plate wasdried overnight, incubated briefly with 25 μL scintillant, and read on aMicro Beta plate reader.

TABLE 1 NET Affinity of Examples 1-11 Example # NET Affinity, μM 1 17.942 <20 3 1.45 4 7.27 5 4.10 6 102.8 7 20.71 8 5.65 9 4.36 10 1.80 1154.85

Examples 13-15 General Procedure for [¹⁸F]Fluorination via[¹⁸F]2-Fluoroethyl Tosylate Part A—Preparation of [¹⁸F]2-FluoroethylTosylate

An MP1 anion exchange cartridge containing 1,000 mCi of [¹⁸F]NaF waseluted with 0.20% aqueous K₂CO₃ (1.0 mL) into a 25 mL conical-bottomedsilanized flask using an automated liquid handling system. The solutionwas evaporated by applying a gentle stream of heated He_((g)) andapplied vacuum. The contents of the flask were reconstituted with 0.5 mLof MeCN, and the MeCN was removed by heated He_((g)) and applied vacuumto eliminate residual H₂O (azeotropic evaporation). A separate 5 mLconical-bottomed Wheaton™ vial was used to prepared a solution of4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (22.5 mg)(referred to as Kryptofix™ and henceforth abbreviated as K₂₂₂) andethylene di-(p-toluenesulfonate) (3.0 mg) in MeCN (1.0 mL). Theconstituents of the vial were transferred to the 25 mL flask containing[¹⁸F]KF, and the flask was positioned inside a microwave cavity (model520 Resonance Instruments, Skokie, Ill.) and subjected to microwaveradiation for 3 min at a power setting of 100 watts. The contents of themicrowave reaction vial were filtered through an anion exchange resin toremove residual fluoride ion and collected in a conical-bottomed 5 mLWheaton™ reaction vial.

Part B—[¹⁸F]Fluorination via [¹⁸F]2-Fluoroethyl Tosylate

The product of Part A was transferred to a conical-bottomed 5 mLWheaton™ reaction vial containing the product of either Example 8,Example 9 or Example 10 (4.0 mg) dissolved in anhydrous DMSO (300 mL).The contents of the vial were heated at 85° C. for 30 min and cooled toambient temperatures. The solution was treated with TFA (1.5 mL) andstirred for 30 min at ambient temperature. The solution was transferredto a clean 25 mL pear-shaped flask and diluted with H₂O (18.5 mL). Thecontents of the pear shaped flask were passed through a Sep Pak™ C18cartridge and the cartridge was rinsed with H₂O (5.0 mL). The desiredproduct was eluted from the cartridge with MeCN (3.0 mL) into aconical-bottomed 5 mL Wheaton™ vial. The product solution was purifiedby HPLC using a Phenomenex LUNA C18(2) column (250×10 mm, 5 micronparticle size, 100 Angstrom pore size) using a 5.0%/min gradient of0-100% ACN containing 0.1% formic acid at a flow rate of 2.0 mL/min. Theproduct eluted from the column in 13-14 min and was collected into apear shaped flask. The solvent was evaporated with gentle heating undervacuum. The contents of the flask were reconstituted with 10% aqueousethanol solution for biological experiments. The final product yield was˜50 mCi (not decay corrected). Radiochemical purity and decay correctedradiochemical yield data is shown in Table 2. Radiosynthesis andpurification time was ˜150 min.

TABLE 2 Radiochemical Yield and Purity Cold Radiochemical RadiochemicalExample # Example # Yield, % Purity, % 13 8 7.4 100 14 9 10.0 100 15 105.0 100

Example 16-22 Synthesis of Fluorinated Piperazines General Synthesis ofFluorinated CAAP Analogs

Substituted anilines can be alkylated with bis(2-chloroethyl)amine atelevated temperatures to yield the phenyl piperazine with the desiredsubstitution pattern on the phenyl ring. The yield for thistransformation is often moderate to low (<50% yield), however variousphenyl piperazines are commercially available. Introduction of theguanidine moiety was carried out via alkylation of the piperazine moietywith N,N-′bis(tert-butoxycarbonyl-1H-pyrazole) 1-carbonxamidine.Deprotection of the guanidine functionality with HCl afforded the finalcompounds, which did not contain a fluoroethoxy moiety. For compoundswhere R is defined as a fluoroethoxy moiety alkylation of the hydroxylprecursor with fluoroethyl tosylate affords the desired substitutionpattern. Typically ¹⁸F compounds are made by the nucleophilicdisplacement of an appropriate leaving group, e.g., tosylate, mesylate,trifluoromethane sulfonate, nitro, trimethyl ammonium or a halide.Alternatively a cyclic sulfate or an epoxide may also be used as aleaving group. Typically these compounds are made from highly activated,dry K¹⁸F, that is made “hotter” by the addition of cryptands such askrytofix[2.2.2]. Purification is generally via salt removal byreverse-phase chromatography (Sep-Pak).

R, R₁ and R₂ are independently selected from the list of H, OR₃, F, Cl,Br, I, CH₂F, OCH₂CH₂F, alkyl (C₁-C₄), aryl, heteroaryl, aralkyl,alkylarl, C(═O)R₃, CO₂R₃, Im, OCH₂CH₂Im, and XIm. Im is an imagingmoiety and may be selected from the group consisting of ¹⁸F, ⁷⁶Br, ¹²⁴I,and ¹³¹I. R₃ may be selected from the same list as R—R₂. The alkyl, arylor heteroaryl substituents in turn may be substituted with alkyl(C₁-C₄),Im, —(CH₂)_(n)Im, CO₂H, halogen (F, Cl, Br, I), OH, NH₂, COOH, Im, COOR,CONR₂, SR, OR or NR₂, in which R may be hydrogen alkyl, aryl oralkylaryl. Under physiological conditions, the guandine/amidinefunctionality of the invention may be protonated; the correspondingsalts of the compounds are also included (hydrochloride, hydrobromide,sulfate, nitrate, alkyl/aryl sulfonates).

Example 16 Synthesis of 4-(4-fluorophenyl)piperazine-1-carboximidamide

To a solution of 4-(fluorophenyl)piperazine (100 mg, 0.56 mmol) anddiisopropylethylamine (106 μL, 0.61 mmol) in ACN (2 mL) was added1H-pyrazole-1-carboximidamide hydrochloride (89 mg, 0.61 mmol). Thereaction stirred at room temperature overnight. A precipitate formed,which was collected via filtration and washed with ACN to obtain4-(4-fluorophenyl)piperazine-1-carboximidamide as a white solid (119 mg,97% yield). ¹H NMR (300 MHz, DMSO-d6): δ 7.77 (br s, 3H), 7.10-6.97 (m,4H), 3.60 (dd, 4H, J=5.3, 4.7 Hz), 3.14 (dd, 4H, J=5.4, 4.7 Hz); ¹³C NMR(75.5 MHz, DMSO-d₆): δ 157.9 (154.8), 156.3, 147.2, 118.0, 115.5(115.2), 48.3, 44.7; ¹⁹F NMR (282.4 MHz, DMSO-d6): δ −124.70-124.78 (m,1F); HRMS calcd for C₁₁H₁₅FN₄: 223.13535 found 223.1353.

Example 17 Synthesis of4-(3-(fluoromethyl)phenyl)piperazine-1-carboximidamide

Synthesis of 4-(3-hydroxymethyl-phenyl)-piperazine-1-carboxylic acidtert-butyl ester

To a solution of 4-(3-formyl-phenyl)-piperazine-1-carboxylic acidtert-butyl ester (2.0 g, 5.98 mmol) in THF (14 mL) at 0° C. was addedLAH (6.0 mL, 1M solution in THF). The reaction mixture stirred at 0° C.for 30 min. followed by a quench of H₂O (239 μL), 15% NaOH (aq., 239μL), and H₂O (718 μL). After completion of the additions the mixturestirred for 20 min. and was then filtered over a pad of celite. Thesolvent of the filtrate was removed en vacuo to obtain4-(3-hydroxymethyl-phenyl)-piperazine-1-carboxylic acid tert-butyl esteras a brown solid (1.47 g, 84% yield), which was taken on to the nextreaction without further purification. ¹H NMR (300 MHz, DMSO-d6): δ 7.17(t, 1H, J=8.0 Hz), 6.91 (br s, 1H), 6.82-6.76 (m, 2H), 5.06 (t, 1H,J=5.80 Hz), 4.44 (d, 2H, J=5.6 Hz), 3.45 (dd, 4H, J=5.5, 4.9 Hz), 3.08(dd, 4H, J=5.3, 5.1 Hz), 1.42 (s, 9H).

Synthesis of tert-butyl4-(3-fluoromethyl-phenyl)-piperazine-1-carboxylic acid tert-butyl ester

To a solution of 4-(3-hydroxymethyl-phenyl)-piperazine-1-carboxylic acidtert-butyl ester (200 mg, 0.68 mmol), triethylamine (143 μL, 1.03 mmol),and tetramethylethylenediamine (10 μL, 0.07 mmol) in toluene (2 mL) at0° C. was added methanesulfonyl chloride (79 μL, 1.03 mmol) drop-wise.After completion of addition the reaction mixture stirred at 0° C. for40 min EtOAc (5 mL) was added to the reaction mixture and the organiclayer was separated, washed with brine, dried over Na₂SO₄, andconcentrated to obtain4-(3-(methanesulfonyloxymethyl-phenyl)-piperazine-1-carboxylic acidtert-butyl ester as a brown oil.

In a Wheaton vial TBAF (268 mg, 1.03 mmol) was added to a solution ofcrude 4-(3-(methanesulfonyloxymethyl-phenyl)-piperazine-1-carboxylicacid tert-butyl ester in ACN (2.3 mL). After completion of addition thereaction mixture was heated to 130° C. for 10 min before being quenchedwith water (1.0 mL). The reaction mixture was extracted with EtOAc(3×5.0 mL) and the organic layers were washed with brine, dried overNa₂SO₄, and concentrated to obtain tert-butyl4-(3-(fluoromethyl)phenyl)piperazine-1-carboxylate along with minorimpurities (201.3 mg, 100% crude yield). ¹H NMR (300 MHz, DMSO-d6): δ7.29-7.24 (m, 1H), 6.99-6.94 (m, 2H), 6.86-6.84 (m, 1H), 5.34 (d, J=48Hz, 2H), 3.47-3.44 (m, 4H), 3.13-3.10 (m, 4H), 1.42 (s, 9H).

Synthesis of 4-(3-(fluoromethyl)phenyl)piperazine-1-carboximidamide

Tert-butyl 4-(3-(fluoromethyl)phenyl)piperazine-1-carboxylate (201.3 mg,mmol) was dissolved in a 4.0 M solution of HCl and dioxane (2 mL) andstirred at room temperature. After 45 min. the reaction mixture wasconcentrated and redissolved in ACN (2 mL). Diisopropylethylamine (22μL, 1.51 mmol) and 1H-pyrazole-1-carboximidamide (110 mg, 0.75 mmol)were added to the stirring reaction mixture. The next day, the reactionmixture was concentrated to yield a crude oil, which was purified byHPLC using a Phenomenex Luna C-18 (2) column (10μ, 250×21.2 mm, gradientmethod 0-100% B over 14 min., where B=90% ACN in water using 0.1% TFA asa modifier and A=water using 0.1% TFA as a modifier) with a flow rate of20 mL/min to isolate4-(3-(fluoromethyl)phenyl)piperazine-1-carboximidamide as a white solid(42.7 mg, 23% isolated yield over 4 steps). ¹H NMR (300 MHz, DMSO-d6): δ7.58 (br s, 3H), 7.28 (t, 1H, J=7.8 Hz), 7.01 (br s, 1H), 6.98 (br s,1H), 6.87 (d, 1H, J=7.3 Hz), 5.35 (d, 2H, J=47.9 Hz), 3.58 (dd, 4H,J=5.4, 4.9 Hz), 3.26 (dd, 4H, J=5.4, 4.8 Hz); ¹³C NMR (75.5 MHz,DMSO-d6): δ 156.1, 150.3, 137.1 (136.8), 129.2, 118.8 (118.7), 115.9,114.9 (114.8), 84.6 (83.4), 47.2, 44.7; HRMS calcd for C₁₂H₁₇FN₄:237.15100 found 237.1514.

Example 18 Synthesis of4-[4-(2-fluoro-ethoxy)-phenyl]-piperazine-1-carboxamidine

Synthesis of tert-butyl4-(4-(2-fluoroethoxy)phenyl)piperazine-1-carboxylate

To a solution of 4-hydroxyphenylpiperazine (2.0 g, 11.22 mmol) in water(56 mL) was added NaOH (673 mg, 16.83 mmol) followed by di-tert-butyldicarbonate (2.7 g, 12.34 mmol). The reaction mixture stirred at roomtemperature overnight. The next day, the reaction mixture was filteredto collect tert-butyl 4-(4-hydroxyphenyl)-piperazine-1-carboxylate as atan solid (3.1 g, 99% yield), which was washed with water (50 mL) andtaken on to the next step without further purification. ¹H NMR (300 MHz,DMSO-d6): δ 6.79 (AA′BB′, 2H, J_(AB)=9.1 Hz, J_(AA′)=2.4 Hz), 6.66(AA′BB′, 2H, J_(AB)=9.1 Hz, J_(BB′)=2.4 Hz), 3.43 (dd, 4H, J=5.3, 4.9Hz), 2.88 (dd, 4H, J=5.2, 5.1 Hz), 1.41 (s, 9H); ¹³C NMR (75.5 MHz,DMSO-d6): δ 153.8, 151.4, 144.0, 118.5, 115.4, 78.8, 50.3, 28.0.

To a solution of tert-butyl 4-(4-hydroxyphenyl)-piperazine-1-carboxylate(1.0 g, 3.59 mmol) in DMSO (12 mL) was added potassium carbonate (745mg, 5.39 mmol), potassium iodide (18 mg, 0.11 mmol) and1-bromo-2-fluoroethane (294 μL, 3.95 mmol). The reaction stirred at 50°C. overnight. The next day, additional amounts of potassium carbonate(745 mg, 5.39 mmol), 1-bromo-2-fluoroethane (134 μL, 1.79 mmol), andpotassium iodide (18 mg, 0.11 mmol) were added. The reaction mixturecontinued to stir at 50° C. After 5 h the reaction mixture was cooled toroom temperature, quenched with water (10 mL), and extracted with EtOAc(3×50 mL). The combined organic layers were washed with water (100 mL),brine (50 mL), dried over Na₂SO₄, and concentrated to obtain a brownsolid. The crude material was purified using silica gel chromatography(1:4 hexanes:EtOAc) to obtain tert-butyl4-(4-(2-fluoroethoxy)phenyl)piperazine-1-carboxylate as a white solid(440 mg, 38% yield). ¹H NMR (300 MHz, DMSO-d6): δ 6.92-6.84 (m, 4H),4.78 (m, 1H), 4.62 (m, 1H), 4.20 (m, 1H), 4.10 (m, 1H), 3.45 (dd, 4H,J=5.2, 5.0 Hz), 2.96 (dd, 4H, J=5.3, 5.0 Hz), 1.42 (s, 9H); ¹⁹F NMR(282.4 MHz, DMSO-d6): δ −222.04 (m, 1F); ¹³C NMR (75.5 MHz, DMSO-d6): δ153.8, 152.1, 145.5, 117.9, 115.1, 83.2 (81.1), 78.9, 67.4 (67.2), 49.7,43.2, 28.0; HRMS calcd. for C₁₇H₂₅FN₂O₃: 325.19220 found 325.19230.

Synthesis of 4-[4-(2-fluoro-ethoxy)-phenyl]-piperazine-1-carboxamidine

A solution of tert-butyl4-(4-(2-fluoroethoxy)phenyl)piperazine-1-carboxylate (440 mg, 1.36 mmol)in 4.0 M HCl in Dioxane (7 mL) stirred for 30 min at room temperature. Aprecipitate formed, which was collected via filtration and washed withDioxane to obtain the desired product as a white powder. The crudematerial was purified on the Prep HPLC using a 0-100% B over 14 minmethod (% B=0.1% TFA in 90% ACN). The pure fractions were collected andlyophilized overnight to afford 1-(4-(2-fluoroethyl)phenyl)-piperazineas a white cake TFA salt (362 mg, 79% yield). ¹H NMR (300 MHz, DMSO-d6):δ 9.00 (br s, 1H), 6.97-6.87 (m, 4H), 4.78 (m, 1H), 4.62 (m, 1H), 4.21(m, 1H), 4.11 (m, 1H); 3.22 (s, 8H) ¹⁹F NMR (282.4 MHz, DMSO-d6): δ−222.07 (m, 1F); ¹³C NMR (75.5 MHz, DMSO-d6): 152.5, 144.5, 118.0,115.2, 83.3 (81.1), 67.4 (67.2), 46.7, 42.8; HRMS calcd. for C₁₂H₁₇FN₂O:225.13977 found: 225.13961.

To a solution of 1-(4-(2-fluoroethoxy)phenyl)piperazine (50 mg, 0.15mmol) and diisopropylethylamine (59 μL, 0.34 mmol) in ACN (1 mL) wasadded 1H-pyrazole-1-carboximidamide (25 mg, 0.17 mmol). The reactionstirred at room temperature for 1 h, monitored by LC-MS. The precipitatewas then filtered and washed with ACN to obtain the desired product as awhite solid (33.8 mg, 58% yield). ¹H NMR (300 MHz, DMSO-d6): δ 7.55 (brs, 3H), 6.95-6.86 (m, 4H), 4.78 (m, 1H), 4.62 (m, 1H), 4.21 (m, 1H),4.11 (m, 1H), 3.57 (dd, 4H, J=5.2, 4.9 Hz), 3.09 (dd, 4H, J=5.1, 5.0Hz); ¹⁹F NMR (DMSO-d6): δ −222.037 (m, 1F); ¹³C NMR (75.5 MHz, DMSO-d6):δ 156.0, 152.2, 144.9, 119.2, 115.1, 82.2 (81.1), 67.4 (67.2), 48.9,44.9; HRMS calcd. for C₁₂H₁₇FN₂O: 267.16157 found 267.16146.

Example 19 Synthesis of4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide

Synthesis of4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide

To a solution of 4-amino-2-chlorophenol (1.0 g, 6.97 mmol) in n-butanol(2 mL) was added bis(2-chloroethyl)amine hydrochloride (1.2 g, 6.97mmol). After completion of addition the reaction mixture was heated atreflux for 60 h. Solid Na₂CO₁ (740 mg, 6.97 mmol) was added to the hotreaction mixture in one portion and the reaction mixture continuedstirring at reflux. After 7 h the reaction mixture was cooled to RT and2-chloro-4-(piperazin-1-yl)phenol was collected via filtration. Thepurple solid was washed with heptanes before proceeding to the next stepwithout further purification (554 mg, 37% yield). ¹H NMR (300 MHz,DMSO-d6): δ 6.95 (dd, 1H, J=2.8, 1.9 Hz), 6.91 (s, 1H), 6.81 (m, 1H),3.21 (m, 4H), 3.16 (m, 4H).

Synthesis of tert-butyl(4-(3-chloro-4-hydroxyphenyl)piperazin-1-yl)methanediylidenedicarbamate

To a solution of 2-chloro-4-(piperazin-1-yl)phenol (200 mg, 0.94 mmol)and diisopropylethylamine (180 μL, 1.03 mmol) in DMF (3 mL) was addedtert-butyl (1H-pyrazol-1-yl)methanediylidenedicarbamate (321 mg, 1.03mmol). After stirring at room temperature for 1.5 h the reaction mixturewas diluted with water (10 mL) and extracted with EtOAc (3×20 mL). Theorganic layers were separated and washed with brine, dried over Na₂SO₄,and concentrated to yield a crude oil. Purification of the crudematerial using silica gel chromatography (gradient of 20 to 100% EtOAcin hexanes) afforded tert-butyl(4-(3-chloro-4-hydroxyphenyl)piperazin-1-yl)methanediylidenedicarbamateas an oil, which crystallized upon standing (186 mg, 43% yield). ¹H NMR(300 MHz, DMSO-d6): δ 9.61 (s, 1H), 9.48 (s, 1H), 6.91 (d, 1H, J=2.8Hz), 6.86 (m, 1H), 6.79 (dd, 1H, J=8.9, 2.8 Hz), 3.50 (dd, 4H, J=5.2,4.3 Hz), 2.99 (dd, 4H, J=5.0, 4.8 Hz), 1.42 (s, 9H), 1.37 (s, 9H); ¹³CNMR (75.5 MHz, DMSO-d6): δ 159.7, 151.2, 150.8, 146.6, 144.5, 119.8,117.9, 116.9, 116.7, 80.1, 77.1, 49.2, 45.3, 27.9 (2C); HRMS calcd. forC₂₁H₃₁ClN₄O₅: 455.20557 found 455.20573.

Synthesis of tert-butyl(4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazin-1-yl)methanediylidenedicarbamate

To a solution of Tert-butyl(4-(3-chloro-4-hydroxyphenyl)piperazin-1-yl)methanediylidenedicarbamate(182 mg, 0.40 mmol) in DMSO (4 mL) was added potassium carbonate (83 mg,0.60 mmol), potassium iodide (3 mg, 0.02 mmol), and1-bromo-2-fluoroethane (33 μL, 0.44 mmol). After completion of theadditions the reaction mixture stirred at 50° C. After 4.5 h thereaction mixture was cooled to room temperature and quenched with water(10 mL). The aqueous layer was extracted with EtOAc (4×20 mL) and allcombined organic layers were washed with water (50 mL), brine (50 mL),dried over Na₂SO₄, and concentrated to yield a crude oil.

Purification of the crude material via HPLC using a Phenomenex Luna C-18(2) column (10μ, 250×21.2 mm, gradient method 40-80% B over 20 min.,where B=90% ACN in water using 0.1% formic acid as a modifier andA=water using 0.1% formic acid as a modifier) with a flow rate of 20mL/min to obtain tert-butyl(4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazin-1-yl)methanediylidenedicarbamateas a white solid (28.8 mg, 12% yield based on recovered startingmaterial). ¹H NMR (300 MHz, DMSO-d6): δ 9.62 (s, 1H), 7.06 (d, 1H, J=9.1Hz), 7.04 (d, 1H, J=2.9 Hz), 6.89 (dd, 1H, J=9.0, 2.9 Hz), 4.75 (m, 1H),4.67 (m, 1H), 4.25 (m, 1H), 4.20 (m, 1H), 3.51 (dd, 4H, J=6.1, 4.1 Hz),3.08 (dd, 4H, J=5.1, 4.8 Hz), 1.42 (s, 9H), 1.37 (s, 9H); ¹⁹F NMR (282.4MHz, DMSO-d6): δ −222.03 (m, 1F); ¹³C NMR (75.5 MHz, DMSO-d6): δ 159.7,151.2, 150.7, 147.1, 145.9, 122.3, 117.9, 115.7, 115.6, 82.1 (81.6),80.1, 77.1, 68.8 (68.7), 48.6, 45.1, 27.9 (2C) Minor rotomericpopulation is also visible; HRMS calcd. for C₂₃H₃₄ClFN₄O₅: 501.22745found 501.2272.

Synthesis of4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide

Tert-butyl(4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazin-1-yl)methanediylidenedicarbamate(26 mg, 0.05 mmol) was dissolved in a 4.0 M solution of HCl in dioxane(0.5 mL) and stirred at room temperature overnight. The next day thereaction mixture was concentrated to yield a crude oil. Purification ofthe crude material via HPLC using a Phenomenex Luna C-18 (2) column(10μ, 250×21.2 mm, gradient method 0-100% B over 14 min, where B=90% ACNin water using 0.1% TFA as a modifier and A=water using 0.1% TFA as amodifier) with a flow rate of 20 mL/min afforded4-(3-chloro-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide as awhite solid (22 mg). ¹H NMR (DMSO-d6): δ 7.53 (br s, 3H), 7.09 (d, 1H,J=2.8 Hz), 7.07 (d, 1H, J=8.1 Hz), 6.93 (dd, 1H, J=9.1, 2.9 Hz), 4.80(m, 1H), 4.64 (m, 1H), 4.28 (m, 1H), 4.18 (m, 1H), 3.55 (dd, 4H, J=5.1,4.9 Hz), 3.14 (dd, 4H, J=5.6, 4.4 Hz); ¹⁹F NMR (282.4 MHz, DMSO-d6): δ−222.03 (m, 1F); ¹³C NMR (75.5 MHz, DMSO-d6): δ 155.9, 147.2, 145.5,122.3, 117.9, 115.8, 115.5, 82.7 (81.6), 68.8 (68.7), 48.1, 44.7; HRMScalcd. for C₁₃H₁₈ClFN₄O: 301.12259 found 301.1225.

Example 20 Synthesis of 4-(3-Bromo-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide

Synthesis of tert-butyl (4-(3-bromo-4-hydroxyphenyl)piperazin-1-yl)methanediylidenedicarbamate

To a solution of the 4-amino-2-bromophenol (1.0 g, 5.32 mmol) inn-butanol (5 mL) was added bis(2-chloroethyl)amine hydrochloride (949mg, 5.32 mmol). After completion of addition, the reaction mixture washeated at reflux for 60 h. Solid Na₂CO₃ (564 mg, 5.32 mmol) was added tothe hot reaction mixture in one portion and the reaction mixturecontinued stirring at reflux. After 7 h the reaction mixture was cooledto RT and 2-bromo-4-(piperazin-1-yl)phenol was collected via filtration.The purple solid was washed with heptanes before proceeding to the nextstep without further purification.

To a solution of 2-bromo-4-(piperazin-1-yl)phenol (500 mg, 1.95 mmol)and diisopropylethylamine (373 μL, 2.14 mmol) in DMF (6 mL) was addedthe ten-butyl (1H-pyrazol-1-yl)methanediylidenedicarbamate (664 mg, 2.14mmol). After stirring at room temperature for 45 min the reactionmixture was diluted with water (20 mL) and extracted with EtOAc (3×50mL). The organic layers were separated and washed with brine, dried overNa₂SO₄, and concentrated to yield a crude oil. Purification of the crudematerial using silica gel chromatography (gradient of 0% to 100% EtOAcin hexanes) afforded tert-butyl(4-(3-bromo-4-hydroxyphenyl)piperazin-1-yl)methanediylidenedicarbamatewas obtained as a white foam (171 mg, 40% yield). ¹H NMR (300 MHz,DMSO-d6): δ 9.64, (br s, 1H), 9.60 (s, 1H), 7.05 (br s, 1H), 6.84 (br s,2H), 3.49 (dd, 4H, J=5.0, 4.4 Hz), 2.99 (dd, 4H, J=4.5, 4.3 Hz),1.44-1.37 (m, 18H); ¹³C (75.5 MHz, DMSO-d6): δ 159.5, 151.2, 150.8,147.7, 144.7, 120.8, 117.5, 116.6, 109.5, 80.1, 77.1, 49.3, 45.3, 27.9(2C); Minor rotomeric population is also visible; HRMS calcd forC₂₁H₃₁BrN₄O₅: 499.15506 found 499.15446.

Synthesis oftert-butyl(4-(3-bromo-4-(2-fluoroethoxy)phenyl)piperazin-1-yl)methanediylidenedicarbamate

To a solution of tert-butyl(4-(3-bromo-4-hydroxyphenyl)piperazin-1-yl)methanediylidenedicarbamate(110 mg, 0.22 mmol) in DMSO (2.2 mL) was added potassium carbonate (46mg, 0.33 mmol), potassium iodide (2 mg, 0.01 mmol), and1-bromo-2-fluoroethane (18 μL, 0.24 mmol). After completion of theadditions the reaction mixture stirred at 50° C. After 6 h the reactionmixture was cooled to room temperature and quenched with water (5 mL).The aqueous layer was extracted with EtOAc (4×20 mL) and all combinedorganic layers were washed with water (50 mL), brine (50 mL), dried overNa₂SO₄, and concentrated to yield a crude oil.

Purification of the crude material via HPLC using a Phenomenex Luna C-18(2) column (10μ, 250×21.2 mm, gradient method 40-80% B over 20 min.,where B=90% ACN in water using 0.1% formic acid as a modifier andA=water using 0.1% formic acid as a modifier) with a flow rate of 20mL/min afforded tert-butyl(4-(3-bromo-4-(2-fluoroethoxy)phenyl)piperazin-1-yl)methanediylidenedicarbamateas a white solid (19 mg, 15% yield). ¹H NMR (300 MHz, DMSO-d6): δ 9.56(s, 1H), 7.05 (d, 1H, J=2.5 Hz), 6.91-6.82 (m, 2H), 4.83 (m, 1H), 4.67(m, 1H), 4.26 (m, 1H), 4.17 (m, 1H), 3.79 (dd, 4H, J=4.7, 4.6 Hz), 3.08(dd, 4H, J=4.5, 4.6 Hz), 1.49 (s, 18H); ¹⁹F NMR (282.4 MHz, DMSO-d6): δ−222.03 (m, 1F); ¹³C NMR (150 MHz, CDCl₃): δ 152.6, 150.9, 150.2, 145.6,122.9, 117.6, 115.8, 113.8, 85.0, 82.5 (81.3), 69.6 (69.4), 50.3, 49.3,27.8; HRMS calcd for C₂₃H₃₄BrFN₄O₅: 501.22745 found 501.2272.

Synthesis of4-(3-bromo-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide

Tert-butyl(4-(3-bromo-4-(2-fluoroethoxy)phenyl)piperazin-1-yl)methanediylidenedicarbamate(26 mg, 0.044 mmol) was dissolved in a 4.0 M solution of HCl in dioxane(0.6 mL) and stirred at room temperature overnight. The next day thereaction mixture was concentrated and purified via HPLC using aPhenomenex Luna C-18 (2) column (10μ, 250×21.2 mm, gradient method40-80% B over 20 min, where B=90% ACN in water using 0.1% formic acid asa modifier and A=water using 0.1% formic acid as a modifier) with a flowrate of 20 mL/min afforded4-(3-bromo-4-(2-fluoroethoxy)phenyl)piperazine-1-carboximidamide as awhite solid (7.4 mg, 44% yield). ¹H NMR (300 MHz, DMSO-d6): δ 8.45 (brs, 3H), 7.22 (d, 1H, J=2.8 Hz), 7.00 (m, 2H), 4.80 (m, 1H), 4.64 (m,1H), 4.28 (m, 1H), 4.18 (m, 1H), 3.52 (dd, 4H, J=5.4, 4.6 Hz), 3.12 (dd,4H, J=5.3, 4.9 Hz); ¹⁹F NMR (282.4 MHz, DMSO-d6): δ −222.03 (m, 1F); ¹³CNMR (75.5 MHz, DMSO-d6): δ 156.7, 148.2, 145.9, 120.8, 116.5, 115.2,111.9, 82.7 (81.6), 68.9 (68.8), 48.3, 44.4; HRMS calcd forC₁₃H₁₈BrFN₄O: 301.12259 found 301.1225.

Example 21 Synthesis of4-(4-((2-fluoroethoxy)methyl)phenyl)piperazine-1-carboximidamide

Synthesis of tert-butyl4-(4-(hydroxymethyl)phenyl)piperazine-1-carboxylate

To a cooled (0° C.) solution of tert-butyl4-(4-formylphenyl)piperazine-1-carboxylate (1.0 g, 3.44 mmol) in ether(17 mL) and THF (3 mL) was added solid lithium borohydride (38 mg, 1.72mmol) in one portion. The reaction mixture stirred for 1 h at 0° C.before being quenched with 1 N HCl to reach pH=7. The resulting organiclayer was filtered through a pad of celite and concentrated to obtaintert-butyl 4-(4-(hydroxymethyl)phenyl)piperazine-1-carboxylate as anorange solid (1 g) ¹H NMR (300 MHz, CDCl₃): δ 7.30 (d, 2H, J=8.6 Hz),6.93 (d, 2H, J=8.6 Hz), 4.61 (d, 2H, J=5.0 Hz), 3.59 (dd, 4H, J=5.3, 5.1Hz), 3.14 (dd, 4H, J=5.2, 5.0 Hz), 1.49 (m, 9H); ¹³C NMR (150 MHz,CDCl₃): δ 154.94, 151.11, 132.92, 128.59, 116.84, 80.14, 65.24, 49.66,43.48, 28.64; Minor rotomeric populations are also visible; HRMS calcdfor C₁₆H₂₄N₂O₃: 293.185969 found 293.18590.

Synthesis of tert-butyl4-(4-((2-fluoroethoxy)methyl)phenyl)piperazine-1carboxylate

To a solution of tert-butyl4-(4-(hydroxymethyl)phenyl)piperazine-1-carboxylate (100 mg, 0.34 mmol)in THF (1 mL) was added triphenylphosphine (135 mg, 0.51 mmol),2-fluoroethanol (24 μL, 0.41 mmol) and diisopropylazodicarboxylate (99μL, 0.51 mmol). The reaction mixture stirred at room temperatureovernight. The next day the reaction mixture was diluted with water (5mL) and extracted with EtOAc (2×10 mL). The combined organic layers werewashed with water (20 mL) and brine (20 mL), dried over Na2SO4, andconcentrated to obtain a crude oil. Purification of the crude materialusing silica gel chromatography (gradient of 0% to 100% EtOAc inhexanes) afforded tert-butyl4-(4-((2-fluoroethoxy)methyl)phenyl)piperazine-1carboxylate as acolorless oil (26 mg, 22% yield). ¹H NMR (300 MHz, CDCl₃) δ 7.27 (d, 2H,J=9.0 Hz), 6.89 (d, 2H, J=9.0 Hz), 4.65 (m, 1H), 4.52 (s, 2H), 4.49 (m,1H), 3.74 (m, 1H), 3.64 (m, 1H), 3.58 (dd, 4H, J=6.0, 3.0 Hz), 3.13 (dd,4H, J=6.0, 3.0 Hz), 1.49 (s, 9H); ¹⁹F NMR (282.4 MHz, CDCl₃): δ −223.01(m, 1F); ¹³C NMR (75.5 MHz, CDCl₃); δ 154.7, 150.9, 129.4, 129.2, 116.5,84.3 (82.0), 79.9, 73.0, 68.8 (68.7), 49.3, 44.0, 28.4; HRMS calcd forC₁₈H₂₇FN₂O₅: 339.20785 found 339.20790.

Synthesis of 1-(4-((2-fluoroethoxy)methyl)-phenyl)piperazinehydrochloride

Tert-butyl 4-(4-((2-fluoroethoxy)methyl)phenyl)piperazine-1-carboxylate(100 mg, 0.29 mmol) was dissolved in a 4.0M solution of HCl in dioxane(1 mL) and stirred at room temperature. After 1 h,1-(4-((2-fluoroethoxy)methyl)-phenyl)piperazine hydrochloride wascollected as a white solid via filtration (74 mg, 91% yield). ¹H NMR(300 MHz, DMSO-d6): δ 10.45 (br s, 1H), 9.71 (br s, 1H), 7.26 (d, 2H,J=8.7 Hz), 7.05 (d, 2H, J=8.7 Hz), 4.61 (m, 1H), 4.45 (m, 1H), 4.43 (s,2H), 3.67 (m, 1H), 3.57 (m, 1H), 3.45 (dd, 4H, J=5.5, 4.9 Hz), 3.22 (m,4H); ¹⁹F NMR (282.4 MHz, CDCl₃): δ −221.40 (m, 1F); ¹³C NMR (75.5 MHz,DMSO): δ 148.5, 130.7, 128.9, 116.4, 84.0 (82.0), 71.7, 68.7 (68.6),46.0, 42.2; HRMS calcd for C₁₃H₁₉FN₂O: 239.15542 found 239.15540.

Synthesis of4-(4-((2-fluoroethoxy)methyl)phenyl)piperazine-1-carboximidamide

To a solution of 1-(4-((2-fluoroethoxy)methyl)-phenyl)piperazinehydrochloride (50 mg, 0.12 mmol) and diisopropylethylamine (67 μL, 0.38mmol) in DMF (1 mL) was added 1H-pyrazole-1-carboximidamidehydrochloride (29 mg, 0.20 mmol). The reaction stirred at roomtemperature for 24 h. The next day, the reaction mixture wasconcentrated to yield a crude oil, which was purified via HPLC using aPhenomenex Luna C-18 (2) column (10μ, 250×21.2 mm, gradient method15-55% B over 20 min., where B=90% ACN in water using 0.1% formic acidas a modifier and A=water using 0.1% formic acid as a modifier) with aflow rate of 20 mL/min afforded4-(4-((2-fluoroethoxy)methyl)phenyl)piperazine-1-carboximidamide as awhite solid (20 mg, 41% yield based on recovered starting material). ¹HNMR (300 MHz, DMSO-d6): δ 7.58 (br s, 4H), 7.211 (d, 2H, J=8.5 Hz), 6.96(d, 2H, J=8.6 Hz), 4.61 (m, 1H), 4.45 (m, 1H), 4.41 (s, 2H), 3.67 (m,1H), 3.58 (dd, 4H, J=4.2, 3.9 Hz), 3.22 (m, 5H); ¹⁹F NMR (282.4 MHz,DMSO-d6): δ −221.39 (m, 1F); ¹³C NMR (75.5 MHz, DMSO-d6): δ 156.1,149.8, 128.9, 115.4, 84.1 (81.9), 71.8, 68.6 (68.4), 47.5, 44.7; HRMScalcd for C₁₄H₂₁FN₄O: 281.177216 found 281.17720.

Example 22 Synthesis of4-(4-(3-fluoropropyl)phenyl)piperazine-1-carboximidamide

Synthesis of tert-butyl 4-(4-iodophenyl)piperazine-1-carboxylate

To a solution of 4-iodophenylpiperazine hydrochloride (1.0 g, 3.08 mmol)in water (15 mL) was added sodium hydroxide (246 mg, 6.16 mmol),followed by di-tert-butyl dicarbonate (740 mg, 3.39 mmol). The reactionmixture stirred at room temperature overnight. The next day, thereaction mixture was filtered to collect tert-butyl4-(4-iodophenyl)piperazine-1-carboxylate as a tan solid (1.1 g, 92%yield), which was washed with water (50 mL) and taken on to the nextstep without further purification. ¹H NMR (600 MHz, CDCl₃): δ 7.53 (d,2H, J=9.0 Hz), 6.68 (d, 2H, J=9.0 Hz), 3.57 (dd, 4H, J=5.2, 5.0 Hz),3.11 (dd, 4H, J=4.9, 4.9 Hz), 1.49 (s, 9H); ¹³C NMR (150 MHz, CDCl₃): δ154.9, 151.1, 138.1, 118.8, 82.3, 80.2, 67.3, 49.2, 28.7; HRMS calcd forC₁₅H₂₁1N₂O₅: 389.07205 found 389.07165.

Synthesis of tert-butyl4-(4-(3-hydroxyprop-1-ynyl)phenyl)piperazine-1-carboxylate

To a slurry of tert-butyl 4-(4-iodophenyl)piperazine-1-carboxylate (200mg, 0.515 mmol), triphenylphosphine (1.4 mg, 0.005 mmol), and palladiumchloride (0.5 mg, 0.003 mmol) in DEA (2 mL) was added DMF (400 μL) andcopper iodide (1 mg, 0.005 mmol). The reaction mixture stirred at roomtemperature for 24 h. The next day, the reaction mixture wasconcentrated and purified using silica gel chromatography (gradientmethod 0%-100% EtOAc in hexanes) to afford tert-butyl4-(4-(3-hydroxyprop-1-ynyl)phenyl)piperazine-1-carboxylate as a yellowsolid (92 mg, 75% yield based on recovered starting material). ¹H NMR(300 MHz, CDCl₃): δ 7.34 (d, 2H, J=8.8 Hz), 6.82 (d, 2H, J=8.9 Hz), 4.48(d, 2H, J=5.6 Hz), 3.57 (dd, 4H, J=5.5, 4.9 Hz), 3.18 (dd, 4H, J=5.4,5.0 Hz), 1.87 (t, 1H, J=5.7 Hz), 1.49 (s, 9H); ¹³C NMR (75 MHz, CDCl₃):δ 154.7, 150.9, 132.8, 115.5, 113.1, 85.9, 80.0, 51.7, 48.4, 44.8, 28.4;HRMS calcd for C₁₈H₂₄N₂O₃: 317.18597 found 317.1861.

Synthesis of tert-butyl4-(4-(3-hydroxypropyl)phenyl)piperazine-1-carboxylate

To a solution of tert-butyl4-(4-(3-hydroxyprop-1-ynyl)phenyl)piperazine-1-carboxylate (3.2 g, 10.11mmol) in EtOH (253 mL) was added EtOAc (200) and Pd/C (10% mol oncarbon, 3.2 g). The reaction mixture was shaken at 50 psi of H₂ atm.overnight. The next day, the catalyst was removed from the reactionmixture via a filtration over a pad of celite and the filtrate wasconcentrated to yield a crude oil. Purification of the crude materialusing silica gel chromatography (gradient method of 0%-100% EtOAc inhexanes) yielded tert-butyl4-(4-(3-hydroxypropyl)phenyl)piperazine-1-carboxylate as an off-whitesolid (2.3 g, 71% yield). ¹H NMR (300 MHz, CDCl₃): δ 7.11 (d, 2H, J=8.7Hz), 6.89 (d, 2H, J=8.7 Hz), 3.67 (br t, 2H, J=6.4 Hz), 3.58 (dd, 4H,J=5.2, 5.1 Hz), 3.09 (dd, 4H, J=5.2, 5.0 Hz), 2.65 (dd, 2H, J=8.0, 7.4Hz), 1.87 (m, 2H), 1.49 (s, 9H); ¹³C NMR (150 MHz, CDCl₃): δ 154.9,149.7, 133.9, 129.3, 117.1, 80.1, 62.4, 49.9, 44.1, 34.5, 31.3, 28.6;HRMS calcd for C₁₈H₂₈N₂O₃: 321.21727 found 321.2174.

Synthesis of tert-butyl4-(4-(3-fluoropropyl)phenyl)piperazine-1-carboxylate

To a solution of deoxofluor (152 μL, 0.69 mmol) in DCM (1.0 mL) at −78°C. was added tert-butyl4-(4-(3-hydroxypropyl)phenyl)piperazine-1-carboxylate (200 mg, 0.625mmol) dissolved in DCM (1.0 mL). After stirring at 0° C. for 1 h thereaction mixture was quenched with saturated NaHCO₃, and extracted withDCM (2×5 mL). All combined organic layers were washed with water (10 mL)and brine (10 mL), dried over Na₂SO₄, filtered, and concentrated toobtain a crude oil. The crude material was purified using silica gelchromatography (0%-100% gradient of EtOAc in Hexanes) to obtaintert-butyl 4-(4-(3-fluoropropyl)phenyl)piperazine-1-carboxylate (78 mg,46% yield was on recovered starting material). ¹H NMR (300 MHz, CDCl₃):δ 7.12 (d, 2H, J=8.7 Hz), 6.89 (d, 2H, J=8.6 Hz), 4.53 (t, 1H, J=6.0Hz), 4.38 (t, 1H, J=6.0 Hz), 3.59 (dd, 4H, J=5.3, 5.1 Hz), 3.10 (dd, 4H,J=5.2, 5.0 Hz), 2.68 (dd, 2H, J=8.1, 7.2 Hz), 2.07-1.90 (m, 2H), 1.49(s, 9H); ¹⁹F NMR (282 MHz, CDCl₃): δ −220.02 (m, 1F); ¹³C NMR (75 MHz,CDCl₃): δ 154.9, 149.8, 133.2, 129.4, 117.1, 84.5 (82.3), 80.1, 49.9,43.9, 32.5 (32.2), 30.6 (30.5), 28.65; HRMS calcd for C₁₈H₂₇FN₂O₂:323.212933 found 323.21320.

Synthesis of 1-(4-(3-fluoropropyl)phenyl)piperazine

Tert-butyl 4-(4-(3-fluoropropyl)phenyl)piperazine-1-carboxylate (78 mg,0.24 mmol) was dissolved in a 4.0M solution of HCl in dioxane (3 mL) andstirred at room temperature. After 1 h1-(4-(3-fluoropropyl)phenyl)piperazine hydrochloride was collected as awhite solid via filtration (63 mg). ¹H NMR (300 MHz, CDCl₃): δ 9.58 (brs, 2H), 9.38 (br s, 1H), 7.15 (d, 2H, J=8.7 Hz), 7.00 (d, 2H, J=8.6 Hz),4.49 (t, 1H, J=6.0 Hz), 4.34 (t, 1H, J=6.0 Hz), 3.40 (dd, 4H, J=5.5, 4.7Hz), 3.22 (br s, 4H), 2.59 (dd, 2H, J=8.1, 6.3 Hz), 1.98-1.80 (m, 2H);¹⁹F NMR (282.4 MHz, CDCl₃): δ −217.98 (m, 1F); ¹³C NMR (75.5 MHz,CDCl₃): δ 147.3, 133.6, 128.9, 116.71, 83.6 (82.5), 46.2, 42.2, 31.5(31.4), 29.7 (29.6); HRMS calcd for C₁₃H₁₉FN₂:223.160503 found223.16060.

Synthesis of 4-(4-(3-fluoropropyl)phenyl)piperazine-1-carboximidamide

To a solution of 1-(4-(3-fluoropropyl)phenyl)piperazine hydrochloride(50 mg, 0.22 mmol) and diisopropylethylamine (82 μL, 0.47 mmol) in DMF(1 mL) was added 1H-pyrazole-1-carboximidamide hydrochloride (36 mg,0.25 mmol). After stirring at room temperature for 9 h, the reactionmixture was purified via HPLC using a Phenomenex Luna C-18 (2) column(10μ, 250×21.2 mm, gradient method 15-55% B over 40 min., where B=90%ACN in water using 0.1% TFA as a modifier and A=water using 0.1% TFA asa modifier) with a flow rate of 20 mL/min afforded4-(4-(3-fluoropropyl)phenyl)piperazine-1-carboximidamide as a whitesolid (36 mg, 42% yield). ¹H NMR (300 MHz, DMSO-d6): δ 7.53 (br s, 3H),7.09 (d, 2H, J=8.6 Hz), 6.92 (d, 2H, J=8.6 Hz), 4.50 (t, 1H, J=6.0 Hz),4.34 (t, 1H, J=6.0 Hz), 3.57 (dd, 4H, J=5.3, 4.8 Hz), 3.17 (dd, 4H,J=5.2, 4.9 Hz), 2.58 (dd, 2H, J=8.1, 6.4 Hz), 1.98-1.80 (m, 2H); ¹⁹F NMR(282.4 MHz, DMSO-d6): δ −217.97 (m, 1F); ¹³C NMR (150 MHz, DMSO-d6): δ156.1, 148.5, 132.1, 128.8, 116.2, 83.6 (82.5), 47.8, 44.8, 31.7 (31.6),29.7 (29.6); HRMS calcd. for C₁₄H₂₁FN₄: 265.18230 found 265.18240.

Examples 23 and 24 Synthesis ofN-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine hydrochloride andN-[3-bromo-4-(3-[18F]fluoropropoxy)-benzyl]-guanidine hydrochloride PartA—Synthesis of 3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-benzaldehyde

To a solution of 3-bromo-4-hydroxy-benzaldehyde (7.14 g, 35.52 mmol)dissolved in DMF (35.5 mL) was added imidazole (5.80 g, 85.24 mmol) andTBDMS-Cl (6.42 g, 42.62 mmol). The reaction mixture stirred for 4 h andwas then diluted with water (50 mL). The aqueous layer was extractedwith EtOAc (3×50 mL). The organic layer was dried over Na₂SO₄ andconcentrated to yield a crude oil. Purification using silica gelchromatography afforded3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-benzaldehyde as a yellow oil(5.13 g, 46% yield). ¹H NMR (CDCl₃, 300 MHz): δ 9.83 (s, 1H), 8.06 (d,J=3.0 Hz, 1H), 7.71 (dd, J=3.0, 9.0 Hz, 1H), 6.97 (d, J=9.0 Hz, 1H),1.17 (s, 9H), 0.28 (s, 6H); ¹³C NMR (CDCl₃, 75 MHz): δ 189.8, 158.3,135.5, 131.5, 130.5, 120.2, 116.6, 25.8, 18.6, −4.0.

Part B—Synthesis of[3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-phenyl]-methanol

To a cooled (0° C.) solution of3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-benzaldehyde (5.13 g, 16.33mmol) dissolved in MeOH (16.5 mL) was added Na₂BH₄ (0.309 g, 8.17 mmol)portion-wise. Once all the reducing agent was added the reaction mixturestirred at room temperature for 30 minutes before being quenched withwater (15 mL). MeOH was removed en vacuo and DCM (20 mL) was added tothe remaining crude reaction mixture. The aqueous layer was extractedwith DCM (3×20 mL). Combined organics were dried over Mg₂SO₄ andconcentrated to yield a crude oil. Purification using silica gelchromatography afforded[3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-phenyl]methanol as acolorless oil (4.22 g, 82% yield). ¹H NMR (CDCl₃, 300 MHz): δ 7.55 (m,1H), 7.17 (dd, J=3.0, 9.0 Hz, 1H), 6.86 (d, J=9.0 Hz, 1H), 4.61 (s, 2H),1.05 (s, 9H), 0.26 (s, 6H); ¹³C NMR (CDCl₃, 75 MHz): δ 152.4, 135.3,132.5, 127.3, 120.5, 115.6, 64.6, 26.0, 18.6, −4.0.

Part C—Synthesis of1,3-bis(tert-butoxy-carbonyl)-[3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-benzyl]-guanidine

To a solution of[3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-phenyl]-methanol (3.11 g,9.84 mmol) dissolved in THF (98.4 mL) was added PPh₃ (3.87 g, 14.76mmol), 1,3 bis(tert-butoxy-carbonyl)guanidine (3.83 g, 11.81), and DIAD(2.86 mL, 14.76 mmol). The reaction mixture stirred at room temperaturefor 30 minutes before being concentrated en vacuo. The resulting yellowoil was purified using silica gel chromatography (4:1 hexanes:EtOAc) toafford1,3-bis(tert-butoxy-carbonyl)-[3-bromo-4-(tert-butyl-dimethyl-silanyloxy)-benzyl]-guanidine(5.14 g, 94% yield). ¹H NMR (CDCl₃, 300 MHz): δ 9.48 (br s, 2H), 7.48(m, 1H), 7.12 (dd, J=3.0, 9.0 Hz, 1H), 6.80 (d, J=9.0 Hz, 1H), 5.07 (s,2H), 1.55 (s, 9H) 10.34 (s, 9H), 1.03 (s, 9H), 0.24 (s, 6H); ¹³C NMR(CDCl₃, 75 MHz): δ 155.0, 151.8, 133.3, 133.0, 127.7, 120.2, 115.0,84.6, 46.8, 28.5, 28.1, 26.0, 18.6, −4.0.

Part D—Synthesis of1,3-bis(tert-butoxy-carbonyl)-[3-bromo-4-hydroxy-benzyl]-guanidine

To a solution of AA (5.14 g, 9.22 mmol) dissolved in THF (92.2 mL) wasadded a solution of TBAF (18.56 mL of 1M THF solution, 18.46 mmol)drop-wise. After completion of addition the reaction mixture continuedto stir at room temperature for 20 minutes. The reaction mixture wasconcentrated en vacuo to yield a crude oil, which was purified usingsilica gel chromatography (4:1 hexanes:EtOAc) to afford a white solid(3.52 g, 88% yield). ¹H NMR (CDCl₃, 300 MHz): δ 9.48 (br s, 2H), 7.45(m, 1H), 7.15 (dd, J=3.0, 9.0 Hz, 1H), 6.92 (d, J=9.0 Hz, 1H), 5.08 (s,2H), 1.52 (s, 9H) 1.42 (s, 9H).

Part E—Synthesis of1,3-bis(tert-butoxy-carbonyl-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine

To a solution of phenol (300 mg, 0.677 mmol) dissolved in DMF (7 mL) wasadded 1-bromo-3-fluoro propane (123.16 mg, 0.880 mmol) and K₂CO₃ (140.3mg, 1.02 mmol). The reaction mixture was heated to 50 C for 2.5 h beforebeing quenched with water (10 mL). The aqueous layer was extracted withEtOAc (20 mL). Organic layer was dried over Na₂SO₄, filtered, andconcentrated to yield a yellow oil. Purification of the crude materialusing silica gel chromatography afforded1,3-bis(tert-butoxy-carbonyl-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine(208.5 mg, 61% yield). ¹H NMR (CDCl₃, 600 MHz): δ 9.43 (br s, 2H), 7.54(m, 1H), 7.54 (d, J=7.8 Hz, 1H), 6.84 (d, J=8.4 Hz, 1H), 5.09 (s, 2H),4.74 (m, 1H), 4.67 (m, 1H), 4.14 (m, 1H), 2.26-2.18 (m, 2H), 1.51 (s,9H) 1.42 (s, 9H); ¹³C NMR (CDCl₃, 150 MHz): δ 155.0, 154.4, 133.2,128.1, 113.2, 111.9, 81.4 (80.3), 65.0 (64.9), 46.8, 30.7 (30.5), 28.5,28.0; ¹⁹F NMR (CDCl₃, 282 MHz): δ −222.68 (m, 1F).

Part F—Example 23—Synthesis ofN-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine hydrochloride

A solution of1,3-bis(tert-butoxy-carbonyl-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine(250.6 mg, 50 mmol) in 4N HCl in dioxane (6 mL) was heated to 50° C. for2 h. The reaction mixture was diluted with water (4 mL) and ACN (1 mL)and lyophilized to affordN-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine hydrochloride as awhite solid (169.1 mg, 99% yield). ¹H NMR (DMSO-d6, 600 MHz): δ 8.03 (brt, 1H), 7.55 (m, 1H), 7.31-7.27 (m, 2H), 7.15 (d, J=9 Hz, 1H), 4.72 (t,J=6 Hz, 1H), 4.56 (t, J=6 Hz, 1H), 4.30 (m, 2H), 4.15 (t, J=6 Hz, 2H),2.19-2.06 (m, 2H).

Part G—Example 24—Synthesis ofN-[3-bromo-4-(3-[18F]fluoropropoxy)-benzyl]-guanidine hydrochloride

To a solution of phenol (3 mg, 6.77 umol) dissolved in acetonitrile (0.7mL) was added 3-[18F]fluoropropyl toluenesulfonate (350 uCi) and K₂CO₃(1.40 mg). The reaction mixture was heated to 80° C. for 45 minutes andcooled to room temperature. The solvent was evaporated in a stream ofwarm nitrogen under partial vacuum. 4N HCl in dioxane (1.0 mL) was addedand the resultant mixture was heated to 50° C. for 15 minutes. Thereaction mixture was diluted with water (15 mL) deposited onto areverse-phase (C-18) cartridge. The salts were removed by washing thecolumn with distilled water, and the compound was eluted with pureacetonitrile (2.0 mL). An aliquot was purified via reversed phase HPLCto afford a ca. 10 mCi sample of pureN-[3-bromo-4-(3-[18F]fluoropropoxy)-benzyl]-guanidine hydrochloride.

Example 25—Animal Preparation

Male Sprague Dawley rats (300-500 g, Taconic), male New Zealand rabbits(3-4 kg, Covance) and male non-human primates (NHP, Cynomolgus monkeys2-4 kg) were used in this study in concordance with our InstitutionalAnimal Care and Use Committee. In tissue biodistribution and imagingstudies, rats were anesthetized with sodium pentobarbital (50 mg/kg,i.p.) and the left femoral vein was canulated with PE50 tubing for druginjection. Rabbits were pre-sedated with acepromazine (0.75 mg/kg i.m.)and then anesthetized with ketamine (40 mg/kg, i.m.) and xylazine (8mg/kg, i.m). The ear marginal vein was canulated for drug injection.NHPs were anesthetized with acepromazine (0.3 mg/kg, i.m.) and ketamine(10 mg/kg, i.m.), orally intubated and maintained with isoflurane(0.4-1.5%). The saphenous vein in the legs was canulated for druginjection. Additional doses of anesthetics were given as needed.

Tissue Biodistribution in Rats and Rabbits

After anesthesia and vein canulation, each animal received a bolusinjection of ¹⁸F labeled agent via the venous catheter. Rats and rabbitswere euthanized after the injection and samples of the blood, heart,lung, liver, spleen, kidney, femur and muscle were collected. Allsamples were weighed and counted for radioactivity (Wallac Wizard 1480,PerkinElmer Life and Analytical Sciences, Shelton, Conn.). The netamount of activity administered in each animal was calculated bysubtracting the residual activities in the syringe and venous catheter.The tissue uptake of each agent was determined as % injected dose pergram tissue (% ID/g).

Cardiac PET Imaging in Animals

Cardiac PET imaging was performed in anesthetized rats, rabbits and NHP.Each animal was anesthetized and a venous catheter was established forimaging agent injection. Then the animal was positioned in a microPETcamera (Focus220, CTI Molecular Imaging, Inc. Knoxyille, Tenn.) forcardiac imaging. Labeled agent was injected intravenously and animalsimaged up to 120 minutes.

Image Reconstruction and Analysis

After the acquisition, images were reconstructed in a matrix of 256×256pixels with 95 transverse slices using the filtered back projectionalgorithm and decay corrected (microPET Manager and ASIPro, CTIMolecular Imaging, Inc. Knoxyille, Tenn.). The pixel size was 0.47 mmand the slice thickness was 0.80 mm. The images were reorientedregarding cardiac axis and serial tomographic cardiac image frames werethen generated for every 10-minute period from 5 to 125 minutes.

FIGS. 1 and 2 represent the images derived from cardiac scanningaccording to the invention.

All publications and patents mentioned in the above specification areherein incorporated by reference. Although the invention has beendescribed in connection with specific preferred embodiments, it shouldbe understood that the invention as claimed should not be unduly limitedto such specific embodiments. Indeed, various modifications of thedescribed modes for carrying out the invention that are obvious to thoseskilled in the relevant fields are intended to be within the scope ofthe following claims.

What is claimed is:
 1. A compound of the structure:

or a salt thereof, wherein n is 0; A and R₂ are absent; X, W, R and R₃are hydrogen; R₁ is NHC(═NH)NH₂; Y is H, F, Cl, or Br; and Z is OR₄ andR₄ is alkyl substituted with ¹⁸F.
 2. A method of imaging cardiacinnervation comprising the steps of: administering an effective amountof the compound of claim 1 or a salt thereof to a patient; detectingradiation emitted by said compound; and forming an image therefrom. 3.The compound of claim 1, wherein the compound is a salt.
 4. The compoundof claim 1, wherein the compound is a salt of a compound selected fromthe group consisting of:


5. A composition for imaging cardiac innervation comprising the compoundof claim 4, and optionally one or more excipients.
 6. A method ofimaging cardiac innervation comprising the steps of: administering aneffective amount of the compound of claim 4 to a patient; detectingradiation emitted by said compound; and forming an image therefrom. 7.The compound of claim 1, wherein the compound is a salt of the compound:


8. The compound of claim 7, wherein the salt has the structureN-[3-bromo-4(3-[18F]fluoropropoxy)-benzyl]-guanidine hydrochloride.
 9. Acomposition for imaging cardiac innervation comprising the compound ofclaim 7, and optionally one or more excipients.
 10. A method of imagingcardiac innervation comprising the steps of: administering an effectiveamount of the compound of claim 7 to a patient; detecting radiationemitted by said compound; and forming an image therefrom.
 11. Acomposition for imaging cardiac innervation comprising the compound ofclaim 1, and optionally one or more excipients.
 12. A compound of thestructure:

or a salt thereof, wherein n is 1; A is absent; R₂ is hydrogen or OR₄,wherein R₄ is H or alkyl; X, W, R and R₃ are hydrogen; R₁ isNHC(═NH)NH₂; Y is H, F, Cl, or Br; and Z is OR₄, wherein R₄ is alkylsubstituted with ¹⁸F.
 13. A compound of the structure:

or a salt thereof, wherein n is 0 or 1; A is absent; R₂, when present,is hydrogen or OR₄, wherein R₄ is H or alkyl; X, W, R and R₃ arehydrogen; R₁ is NHC(═NH)NH₂; Z is H, F, Cl, or Br; and Y is OR₄, whereinR₄ is alkyl substituted with ¹⁸F.
 14. A compound of the structure:

or a salt thereof, wherein n is 0 or 1; R is NR₄C(═NR₅)NHR₆; R₁ isselected from the group consisting of H and alkyl (C₁-C₄); when present,R₂ is H or OR₄ R₃ is H; R₄, R₅, and R₆ are independently selected fromthe group consisting of H and alkyl (C₁-C₈), wherein one or more R₄-R₆may be substituted with an imaging moiety; A is absent; W and X arehydrogen; and Y and Z are independently selected from the groupconsisting of H, OR₄, F, Cl, Br, and I, wherein Y or Z is OR⁴ and R⁴ isalkyl substituted with ¹⁸F.
 15. The compound of claim 14, wherein thecompound has the structure:

or a salt thereof.
 16. A method of imaging cardiac innervationcomprising the steps of: administering an effective amount of thecompound of claim 12 or a salt thereof to a patient; detecting radiationemitted by said compound; and forming an image therefrom.
 17. A methodof imaging cardiac innervation comprising the steps of: administering aneffective amount of the compound of claim 13 or a salt thereof to apatient; detecting radiation emitted by said compound; and forming animage therefrom.
 18. A method of imaging cardiac innervation comprisingthe steps of: administering an effective amount of the compound of claim15 or a salt thereof to a patient; detecting radiation emitted by saidcompound; and forming an image therefrom.
 19. A method of imagingcardiac innervation comprising the steps of: administering an effectiveamount of the compound of claim 14 or a salt thereof to a patient;detecting radiation emitted by said compound; and forming an imagetherefrom.
 20. The compound of claim 13, wherein n is
 0. 21. Thecompound of claim 14, wherein n is
 0. 22. The compound of claim 13,wherein n is
 1. 23. The compound of claim 14, wherein n is 1.